WO2009119765A1 - Wireless communication device and communication device - Google Patents

Wireless communication device and communication device Download PDF

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Publication number
WO2009119765A1
WO2009119765A1 PCT/JP2009/056178 JP2009056178W WO2009119765A1 WO 2009119765 A1 WO2009119765 A1 WO 2009119765A1 JP 2009056178 W JP2009056178 W JP 2009056178W WO 2009119765 A1 WO2009119765 A1 WO 2009119765A1
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WO
WIPO (PCT)
Prior art keywords
handover
wireless communication
communication network
unit
time
Prior art date
Application number
PCT/JP2009/056178
Other languages
French (fr)
Japanese (ja)
Inventor
知津子 長澤
空悟 守田
Original Assignee
京セラ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 京セラ株式会社 filed Critical 京セラ株式会社
Priority to US12/934,586 priority Critical patent/US20110026494A1/en
Priority to JP2010505794A priority patent/JP5002707B2/en
Publication of WO2009119765A1 publication Critical patent/WO2009119765A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/02—Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/04—Arrangements for maintaining operational condition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0011—Control or signalling for completing the hand-off for data sessions of end-to-end connection
    • H04W36/0016—Hand-off preparation specially adapted for end-to-end data sessions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
    • H04W36/302—Reselection being triggered by specific parameters by measured or perceived connection quality data due to low signal strength
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/06—Terminal devices adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/14—Reselecting a network or an air interface

Definitions

  • the present invention relates to a wireless communication apparatus capable of performing handover between different wireless communication networks, and a communication apparatus communicating with the wireless communication apparatus.
  • IP mobility technology that enables handover between different wireless communication networks, such as mobile phone networks and wireless LANs, in order to realize a ubiquitous environment.
  • mobile IP Mobile IPv4 and Mobile IPv6
  • NEMO Network Mobility
  • a mobile node MN: Mobile Node
  • the home agent HA: Home Agent
  • CoA Care of
  • CN counterpart node
  • an MBB Make-Before-Break method in which a handover destination network is connected before disconnecting the handover source network, or a handover destination network is connected after disconnecting the handover source network.
  • a BBM Block-Before-Make
  • the HA receives Registration Request (Binding Update in NEMO) that is handover request information from the MN, and registers the handover destination CoA. Communication is performed between the MN and the CN via the wireless communication network. Further, the MN receives Registration Reply (Binding Acknowledge in NEMO), which is handover completion information returned from the HA, and disconnects from the handover source wireless communication network. Communication is performed via a wireless communication network.
  • the MN transmits a packet from the handover source wireless communication network.
  • the absolute delay time of the handover source downlink is longer than the absolute delay time of the handover destination downlink
  • the wireless communication network is switched based on the handover completion information from the handover destination, after the switching, the packet transmitted from the HA via the handover source wireless communication network is disconnected from the handover source wireless communication network.
  • the packet cannot be received and the packet is lost.
  • the lost amount of this packet increases as the absolute delay time of the downlink from the HA to the MN in the handover source wireless communication network is longer than that in the handover destination wireless communication network.
  • a first object of the present invention made in view of such a point is to provide a wireless communication apparatus that can be handed over to a different wireless communication network without causing packet loss and can always maintain stable reproduction quality and real-time performance. There is.
  • a second object of the present invention is to provide a communication device that can transmit a packet without causing packet loss to a wireless communication device handed over to a different wireless communication network, and can always maintain stable reproduction quality and real-time performance. It is to provide.
  • the invention of the wireless communication apparatus for achieving the first object is as follows: A wireless communication unit that performs wireless communication by connecting to a first wireless communication network and a second wireless communication network different from the first wireless communication network; An execution unit that executes an application of a real-time communication system via the wireless communication unit; A communication quality acquisition unit for acquiring communication quality of a radio link in the first wireless communication network while executing the application by connecting to the first wireless communication network; A determination unit that determines whether to start preparation for handover from the first wireless communication network to the second wireless communication network based on the communication quality acquired by the communication quality acquisition unit; When the determination unit determines the start of handover preparation, the data is transmitted through the first wireless communication network, the data is stored for a predetermined time, and after the handover, the stored data is transferred to the second wireless communication network.
  • a control unit controlling to transmit via, It is characterized by providing.
  • the invention according to a second aspect is the wireless communication device according to the first aspect,
  • an estimation unit that estimates a handover preparation time until the handover is started based on the communication quality acquired by the communication quality acquisition unit;
  • a measurement unit that measures respective delay times in the first wireless communication network and the second wireless communication network, and
  • the control unit accumulates the data based on respective delay times in the first wireless communication network and the second wireless communication network measured by the measurement unit and the handover preparation time estimated by the estimation unit. It is characterized by determining a start time to be performed.
  • the invention according to a third aspect is the wireless communication device according to the first aspect,
  • a measurement unit that measures respective delay times in the first wireless communication network and the second wireless communication network, and
  • the control unit determines a predetermined time for storing the data based on respective delay times in the first wireless communication network and the second wireless communication network measured by the measurement unit. is there.
  • the invention according to a fourth aspect is the wireless communication device according to the first, second or third aspect, An encoding unit for encoding transmission data;
  • the encoding unit encodes the accumulated data at a rate lower than an encoding bit rate before the determination unit determines start of handover preparation.
  • the invention of the communication device is as follows: A communication unit that connects to a communication network and executes communication; An execution unit that executes an application of a real-time communication system via the communication unit; When a wireless communication device that is a communication partner of the application receives handover information from the wireless communication device that performs handover from the first wireless communication network in communication to a second wireless communication network different from the first wireless communication network, A control unit for transmitting data via a communication network, storing the data for a predetermined time, and controlling the stored data to be transmitted to the wireless communication device after handover of the wireless communication device; It is characterized by providing.
  • the invention according to a sixth aspect is the communication apparatus according to the fifth aspect,
  • the control unit based on the handover preparation time, the delay time in the first radio communication network and the second radio communication network, and the delay time in the communication network, included in the handover information, A start time for storing the data is determined.
  • the invention according to a seventh aspect is the communication apparatus according to the fifth aspect,
  • the control unit determines a predetermined time for storing the data based on respective delay times in the first wireless communication network and the second wireless communication network included in the handover information. Is.
  • the invention according to an eighth aspect is the communication apparatus according to the sixth aspect,
  • the control unit determines a predetermined time for storing the data based on respective delay times in the first wireless communication network and the second wireless communication network included in the handover information. Is.
  • the invention according to a ninth aspect is the communication device according to the fifth, sixth, seventh or eighth aspect, An encoding unit for encoding transmission data;
  • the encoding unit encodes the accumulated data at a rate lower than an encoding bit rate before receiving the handover information.
  • the wireless communication device of the present invention determines to start preparation for handover from the first wireless communication network to the second wireless communication network, transmits data via the first wireless communication network and stores the data for a predetermined time. Then, the stored data is transmitted via the second wireless communication network after the handover. Therefore, it is possible to accumulate while transmitting data for a predetermined time that is thought to be lost due to handover, and transmit the accumulated data after the handover. As a result, handover to a different wireless communication network can be performed without causing packet loss, and stable reproduction quality and real-time performance can always be maintained.
  • the communication apparatus of the present invention receives information on handover from the first wireless communication network with which the wireless communication apparatus is communicating to another second wireless communication network from the wireless communication apparatus that is the communication partner, While transmitting data to the communication device, the data is stored for a predetermined time, and the stored data is transmitted after the handover of the wireless communication device. Therefore, based on the handover information from the wireless communication device, the wireless communication device accumulates while transmitting data for a predetermined time that is considered to be lost when the wireless communication device hands over to a different wireless communication network, and the stored data is handed over. Can be sent later. As a result, stable reproduction quality and real-time performance can always be maintained without causing packet loss.
  • FIG. 3 is a diagram for explaining a method for calculating a handover preparation time by the handover control unit shown in FIG. 2. It is a figure for demonstrating an example of the absolute delay time acquisition method.
  • FIG. 3 is a diagram illustrating an example of a conversion table between radio conditions and throughput stored in a handover control unit illustrated in FIG. 2.
  • FIG. 2 is a sequence diagram for explaining a handover process between the wireless communication apparatus shown in FIG. 1 and an HA. It is a figure for demonstrating generation
  • FIG. 4 is a flowchart showing an operation at the time of handover by a transmission control unit shown in FIG. 3.
  • FIG. It is a figure which shows the state of the transmission / reception packet between communication apparatuses when the radio
  • FIG. 2 is a sequence diagram illustrating a flow of handover information between the wireless communication device, the HA, and the communication device illustrated in FIG. 1.
  • 15 is a flowchart showing an operation of a reproduction speed calculation unit shown in FIG. It is a figure for demonstrating the reproduction
  • FIG. 15 is a diagram for describing an example of a reception packet reproduction rate control method by the jitter buffer control unit illustrated in FIG. 14. It is a figure which shows schematic structure of the communication network which can use the communication apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram which shows schematic structure of the radio
  • FIG. 31 is a sequence diagram showing an operation of a main part of the telephone function unit shown in FIG. 30. It is a figure for demonstrating the reproduction
  • FIG. 1 is a diagram showing a schematic configuration of a communication network that can be used by the wireless communication apparatus according to the first embodiment of the present invention.
  • a wireless communication device (MN) 11 that is a mobile node makes a call with a communication device (CN) 12 that is an opposite node by VoIP that is a real-time communication system application.
  • the wireless communication device 11 can be handed over between the first wireless communication network 15 and the second wireless communication network 16.
  • the first wireless communication network 15 and the second wireless communication network 16 are coupled to the Internet 18.
  • the first wireless communication network 15 is assumed to be, for example, a mobile phone network of cdma2000 1xEV-DO (Code Division Multiple Access 2000-1x Evolution Data Only), and the second wireless communication network 16 is, for example, a wireless LAN (Local Area Network). ) Is assumed. It is assumed that the uplink absolute delay time in the second radio communication network 16 is shorter than the uplink absolute delay time in the first radio communication network 15.
  • reference numeral 15 a indicates a base station of the first wireless communication network 15, and reference numeral 16 a indicates an access point of the second wireless communication network 16.
  • the communication device 12 includes, for example, a personal computer to which a handset 12a is connected and a softphone as a telephone function unit is installed, and is connected to the Internet 18 through an Internet service provider (not shown).
  • SIP Session Initiation Protocol
  • SIP server 21 and 22 for controlling communication are connected to the first wireless communication network 15 and the second wireless communication network 16, respectively.
  • a home agent (HA) 23 that transfers a received packet addressed to the wireless communication device 11 to the wireless communication network to which the wireless communication device 11 is connected and a SIP server 24 that controls communication are connected to the Internet 18.
  • the home address used in the wireless communication network to which the wireless communication apparatus 11 originally belongs is registered in the HA 23, and the IP address of the handover destination wireless communication network is taken care of (CoA: care) at the time of handover.
  • CoA care
  • handover between different wireless communication networks becomes possible.
  • IP mobility technology is well known in the above-described mobile IP and NEMO, and thus detailed description thereof is omitted here.
  • the wireless communication device 11 registers the IP address of the first wireless communication network 15 in the HA 23 as a care-of address (first wireless CoA), and communicates with the communication device 12 via the first wireless communication network 15. It is assumed that handover is performed from the current state to the second wireless communication network 16.
  • FIG. 2 is a functional block diagram showing a schematic configuration of the wireless communication apparatus 11 according to the present embodiment shown in FIG.
  • the wireless communication device 11 executes a first wireless I / F (interface) 31 corresponding to the first wireless communication network 15, a second wireless I / F 32 corresponding to the second wireless communication network 16, and a VoIP application.
  • the wireless information of the telephone function unit 33, the communication processing unit 34 that controls connection to the first wireless communication network 15 and the second wireless communication network 16, and the wireless information of the first wireless communication network 15 and the second wireless communication network 16 is acquired.
  • a wireless information acquisition unit 35; and a handover control unit 36 that controls a handover between the first wireless communication network 15 and the second wireless communication network 16.
  • the communication processing unit 34 constitutes a wireless communication unit that performs wireless communication, and calls between the telephone function unit 33 and the communication device 12 via the first wireless communication network 15 or the second wireless communication network 16. And the connection of the first wireless I / F 31 or the second wireless I / F 32 is controlled to communicate with the HA 23 under the control of the handover control unit 36.
  • the wireless information acquisition unit 35 acquires the communication quality of the corresponding first wireless communication network 15 and second wireless communication network 16 from the first wireless I / F 31 and the second wireless I / F 32 as wireless information,
  • the acquired communication quality is supplied to the handover control unit 36.
  • the communication quality for example, RSSI (Received Signal Signal Strength Indicator) indicating a wireless state is acquired. Therefore, the radio information acquisition unit 35 constitutes a communication quality acquisition unit that acquires the communication quality of the radio link.
  • the handover control unit 36 Based on the communication quality from the radio information acquisition unit 35, the handover control unit 36 generates handover information including a decision whether to schedule a handover, that is, whether to start preparation for handover, and the handover information Based on the above, handover is controlled.
  • FIG. 3 is a functional block diagram showing a schematic configuration of the telephone function unit 33 of the wireless communication apparatus 11 shown in FIG.
  • the telephone function unit 33 is composed of, for example, a soft phone, and has a button input unit 41, a screen display unit 42, a microphone 43, an encoder 44, a packet transmission unit 45, a packet reception unit 46, a jitter buffer, as in the configuration of a known soft phone. 47, a decoder 48, a speaker 49, a jitter buffer monitoring unit 50, a jitter buffer control unit 51, a SIP control unit 52, and an overall control unit 53 for controlling the overall operation.
  • the overall control unit 53 acquires user operation information via the button input unit 41 and the screen display unit 42, and controls the overall operation based on the acquired information.
  • the SIP control unit 52 controls SIP procedures for starting and ending a call.
  • the audio data acquired from the microphone 43 is encoded by the encoder 44 which is an encoding unit, and the encoded data is put into a packet from the packet transmission unit 45 and communicated via the communication processing unit 34. Transmitted to the device 12.
  • the packet from the communication device 12 received by the packet receiving unit 46 via the communication processing unit 34 is once fetched into the jitter buffer 47 and then read out. Are decoded and output as reproduced sound from the speaker 49.
  • the reception status of packets in the jitter buffer 47 and the number of packets (data amount) in the jitter buffer 47 are monitored by the jitter buffer monitoring unit 50. Based on the monitoring result, the jitter buffer control unit 51 Processing such as a packet reading speed from the jitter buffer 47 and discarding of the received packet is controlled.
  • the radio communication apparatus 11 further includes a telephone function unit 33, a handover information acquisition unit 55, a transmission control unit 56, and a transmission buffer 57.
  • the handover information acquisition unit 55 monitors handover information from the handover control unit 36 at regular intervals, and acquires handover schedule determination information for determining a handover schedule. When the handover schedule determination information is acquired, the handover information acquisition unit 55 further acquires the required handover information from the handover control unit 36 and supplies the acquired required handover information to the transmission control unit 56.
  • the transmission control unit 56 controls the encoding bit rate of transmission data by the encoder 44 and the transmission of data from the encoder 44 to the packet transmission unit 45. That is, the transmission control unit 56 directly transmits the data encoded by the encoder 44 to the packet transmission unit 45 in a normal call state in which handover information is not supplied from the handover information acquisition unit 55. On the other hand, when the handover information is supplied from the handover information acquisition unit 55, the transmission control unit 56 stores the data from the encoder 44 that seems to be lost due to the handover in the transmission buffer 57 based on the handover information. The accumulated data is controlled to be transmitted to the packet transmitter 45 after the handover is completed. The transmission control by the transmission control unit 56 will be further described later.
  • the telephone function unit 33 configures an execution unit that executes a real-time communication system application and a control unit that controls transmission of data of the application.
  • the handover control unit 36 determines a handover schedule based on the communication qualities acquired from the first wireless I / F 31 and the second wireless I / F 32 via the wireless information acquisition unit 35, respectively. For example, when a call is made by forming a wireless link with the first wireless communication network 15, the communication quality acquired from the first wireless I / F 31 becomes worse than the handover schedule determination threshold, and the second wireless I / F When the communication quality of F32 is equal to or higher than the handover schedule determination threshold, the handover control unit 36 determines the handover schedule to the second wireless communication network 16, that is, determines the start of handover preparation.
  • the communication quality of the second wireless communication network 16 that is not used for a call is acquired (measured) by receiving broadcast information transmitted from the access point 16a, for example.
  • the handover preparation time Ts (sec), which is the time until the start of the handover, that is, the time until the Registration Request (Binding Update in NEMO) is transmitted,
  • the predicted bandwidth Rbup2 (bps) the predicted bandwidth
  • handover control unit 36 supplies the obtained information to the telephone function unit 33 as necessary handover information including handover schedule determination information indicating handover schedule determination.
  • the telephone function unit 33 transmits the required handover information among the handover information acquired from the handover control unit 36 to the communication apparatus 12 via the HA 23 as a handover advance notice message. Therefore, in radio communication apparatus 11 according to the present embodiment, handover control unit 36 includes a determination unit that determines whether to start preparation for handover, an estimation unit that estimates handover preparation time, and the first radio communication network. 15 and the measurement part which measures each delay time in the 2nd radio
  • the handover preparation time Ts is calculated based on a unit time change rate ⁇ Rs (slope) of the radio state (Rs) for determining communication quality.
  • the rate of change ⁇ Rs can be measured and acquired when the radio state falls below the handover schedule determination threshold and the handover schedule is determined, but in this embodiment, the handover schedule determination is performed during the call.
  • the change rate average value ⁇ Rsrms from the time point to a predetermined time before is acquired.
  • the handover control unit 36 calculates the change rate ⁇ Rs (t) of the unit time ( ⁇ t) of the radio state in the currently used radio communication network according to the following formula at a predetermined timing, A plurality of change rates ⁇ Rs (t) up to 2 seconds before) are held in the memory.
  • the change rate average value ⁇ Rsrms up to a predetermined time held at that time is calculated.
  • the handover control unit 36 determines whether or not the calculated change rate average value ⁇ Rsrms is smaller than a preset change rate threshold value Rsref.
  • the handover preparation time Ts is set to a preset standard time Tref (for example, 5 sec). To do.
  • Ts Tref (Rsref / ⁇ Rsrms) is calculated, and the higher the rate of change ⁇ Rsrms, the greater the handover preparation time Ts. Is set shorter than the standard time Tref.
  • FIG. 4B shows a case where ⁇ Rsrms> Rsref and the handover preparation time Ts is set to approximately half the standard time Tref (2.5 sec).
  • the handover source uplink absolute delay time Tdup1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2 between the wireless communication apparatus 11 and the HA 23 are, for example, any of the first to third absolute delay time acquisition methods described below. Get by.
  • the handover control unit 36 determines a handover schedule
  • the handover control unit 36 synchronizes with the radio communication apparatus 11 via the first radio I / F 31 and the second radio I / F 32 in time synchronization.
  • the HA 23 transmits a measurement packet having a transmission time stamp, and requests the HA 23 to return a measurement packet having the transmission time stamp, the reception time stamp at the HA 23, and a return time stamp from the HA 23. Thereby, the measurement packet is transmitted from both the first wireless communication network 15 and the second wireless communication network 16 from the HA 23.
  • the wireless communication device 11 receives the measurement packet transmitted from the HA 23 via the corresponding first wireless I / F 31 and second wireless I / F 32, respectively, and based on the reception time and the time stamp of the measurement packet. Measure absolute delay times Tdup1, Tdup2, and Tddn2 of the corresponding network.
  • the handover control unit 36 determines a handover schedule
  • the handover control unit 36 transmits a first wireless communication network from the wireless communication device 11 to the HA 23 that is time-synchronized with the wireless communication device 11.
  • 15 and the second wireless communication network 16 transmit measurement packets such as PING and RTCP, receive the reply, and measure the absolute delay times Tdup1, Tdup2, and Tddn2 of the corresponding networks.
  • the handover control unit 36 determines a handover schedule, acquires the absolute delay time of each wireless communication network by using a handover technique studied in IEEE 802.21.
  • IEEE 802.21 Media Independent Handover (MIH)
  • MIH Media Independent Handover
  • WiFi Wireless Fidelity
  • WiMAX Worldwide Interoperability for Microwave Access
  • mobile phones etc.
  • the handover control unit 36 is defined as an MIH user, and MIHF (MIH Function) acquires wireless information of a communication device based on a request from the MIH user and provides it to the MIH user.
  • MIHF MIH Function
  • FIG. 5 is a diagram for explaining the third absolute delay time acquisition method.
  • a measurement server 61 that operates to measure delay time is connected to the Internet 18 that is a backbone network, and a first information server 62 is connected to the first wireless communication network 15.
  • a second information server 63 is connected to the second wireless communication network 16.
  • the first information server 62 includes a network delay reference time Tn1 as a reference for delay time measurement from the measurement server 61 directly connected to the Internet 18 to the base station 15a, and upper and lower distances from the base station 15a to the wireless communication device 11. Holds radio delay reference times Trup1 and Trdn1.
  • the second information server 63 holds the network delay reference time Tn2 from the measurement server 61 to the access point 16a, and the upper and lower radio delay reference times Trup2 and Trdn2 from the access point 16a to the wireless communication device 11.
  • the network delay reference times Tn1 and Tn2 are transmitted and received between the base station 15a and the measurement server 61, and between the access point 16a and the measurement server 61, respectively (such as PING and RTCP).
  • the round trip time is measured, and the round trip time is halved.
  • the upper and lower radio delay reference times Trup1 and Trdn1 in the first radio communication network 15 send a packet from the base station 15a to the radio communication device 11, and the radio communication device 11 that has received the packet records and returns the received time.
  • the respective uplink and downlink delay times are calculated based on the times transmitted and received between the base station 15a and the wireless communication device 11.
  • the upper and lower radio delay reference times Trup2 and Trdn2 in the second radio communication network 16 send a packet from the access point 16a to the radio communication device 11, and the radio communication device 11 that receives the packet records the received time. By sending it back, each of the uplink and downlink delay times is calculated based on the time transmitted and received between the access point 16a and the wireless communication device 11.
  • Trup1 and Trup2 indicate uplink radio delay reference times
  • Trdn1 and Trdn2 indicate downlink radio delay reference times.
  • the handover control unit 36 of the wireless communication device 11 When connecting to the first wireless communication network 15 that is the handover source, the handover control unit 36 of the wireless communication device 11 sends a network delay from the first information server 62 connected to the first wireless communication network 15 via the MIHF. The reference time Tn1 and the radio delay reference times Trdn1 and Trup1 are acquired. Further, the handover control unit 36 transmits / receives a packet to / from the other party (here, the HA 23) whose delay time is to be measured, and the round-trip time (Tn3 + Trdn3 + Tn3 + Trup3) between the other party and its own wireless communication device 11 ).
  • the other party here, the HA 23
  • the handover controller 36 obtains a one-way delay time (Tn3-Tn1) between the HA 23 and the Internet 18 from this value as follows, and performs a handover between the wireless communication apparatus 11 and the HA 23.
  • Tn3 + Trup3 corresponding to the original upstream absolute delay time Tdup1 is calculated.
  • Tn3-Tn1 ⁇ (Tn3 + Trdn3 + Tn3 + Trup3)-(Tn1 + Trdn1 + Tn1 + Trup1) ⁇ / 2
  • the handover control unit 36 acquires the network delay reference time Tn2 and the radio delay reference times Trup2 and Trdn2 of the handover destination. Therefore, the location information of the wireless communication device 11 is transmitted to the second information server 63 of the second wireless communication network 16 that is the handover destination via the first information server 62 of the first wireless communication network 15 that is currently connected. To request a reply of the network delay reference time Tn2 and the radio delay reference times Trup2 and Trdn2. As a result, the second information server 63 determines the network delay reference time Tn2 and the radio delay reference times Trup2 and Trdn2 of the access point 16a that is considered to be connected in consideration of the position information and the number of connected users of each access point. The response is made to the wireless communication device 11 via the first information server 62.
  • the handover controller 36 receives the handover destination network delay reference time Tn2 and the radio delay reference times Trup2, Trdn2 returned from the second information server 63, and uses the obtained information and the calculated (Tn3-Tn1). In the following manner, Tn4 + Trup4 corresponding to the handover destination uplink absolute delay time Tdup2 and Tn4 + Trdn4 corresponding to the downlink absolute delay time Tddn2 between the wireless communication apparatus 11 and the HA 23 are calculated.
  • the handover control unit 36 stores the absolute delay times Tdup1, Tdup2, and Tddn2 acquired by any of the first to third absolute delay time acquisition methods in the memory (see FIG. (Not shown).
  • the uplink predicted bandwidth Rbup2 of the handover destination is obtained by predicting the uplink radio state in the handover destination radio communication network after completion of the handover. For this reason, the handover control unit 36 stores, for example, a conversion table between the wireless state (communication quality) and the throughput (predicted bandwidth) as shown in FIG. For example, the handover control unit 36 linearly predicts the handover destination radio status at the completion of the handover based on the handover destination radio status at the time when the handover schedule is determined and the handover destination radio status a predetermined time before that time.
  • the handover completion time point is the round-trip time between the HA 23 and the wireless communication device 11 in the handover destination wireless communication network (here, the second wireless communication network 16) from the handover schedule determination time point.
  • the absolute delay time (Trup2 + Trdn2) is added.
  • the handover control unit 36 acquires the handover preparation time Ts, the handover source uplink absolute delay time Tdup1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, and the handover destination predicted bandwidth Rbup2. Is acquired to the telephone function unit 33.
  • the handover control unit 36 determines a handover schedule, the handover control unit 36 executes a handover process.
  • FIG. 7 is a sequence diagram for explaining a handover process between the wireless communication apparatus 11 and the HA 23.
  • the handover control unit 36 of the wireless communication device (MN) 11 determines a handover schedule
  • the handover control unit 36 controls the communication processing unit 34 to transfer the second wireless I / F 32 to the second wireless communication network 16. Connecting. Thereafter, when the handover preparation time Ts elapses, the handover control unit 36 transmits a Registration Request (in NEMO, Binding Update) to the HA 23 via the second wireless communication network 16 that is the handover destination.
  • the handover control unit 36 transmits the handover request information to the HA 23
  • the handover control unit 36 transmits a handover schedule notification indicating the fact to the telephone function unit 33 as the handover information.
  • the HA 23 Upon receipt of the handover request information, the HA 23 registers the IP address of the handover destination as a care-of address (second wireless CoA), and registers Registration Reply (Binding Acknowledge in NEMO) as the second wireless communication network. 16 is sent back to the wireless communication apparatus 11 via 16. Note that the HA 23 registers only one care-of address with the wireless communication device 11. Therefore, the care-of address of the handover destination (second radio CoA) is registered by overwriting the care-of address of the handover source (first radio CoA) already registered. When the care-of address of the handover destination is registered, the HA 23 accepts only the packet from the registered care-of address (second wireless CoA) from that point, and the packet whose source is the previous care-of address (first wireless CoA) Not accepted.
  • the handover control unit 36 After receiving RegistrationRegReply (Binding Acknowledge in NEMO) as handover completion information sent back from the HA 23, the handover control unit 36 starts transmission / reception of packets by the second wireless communication network 16 as the handover destination, and performs communication.
  • the processing unit 34 is controlled to disconnect the connection between the first wireless I / F 31 and the first wireless communication network 15 that is the handover source.
  • the handover control unit 36 transmits a handover completion notification indicating the fact to the telephone function unit 33 as the handover information.
  • the HA 23 does not accept a transmission packet from the handover source after registering the IP address of the handover destination as the care-of address (second wireless CoA). For this reason, of the packets transmitted from the wireless communication device 11 to the HA 23 via the first wireless communication network 15 that is the handover source, the packet that arrives at the HA 23 after the handover request information reaches the HA 23 is lost. Become.
  • FIG. 8 is a diagram for explaining the occurrence of packet loss in this case.
  • NEMO will be described as an example.
  • the HA 23 receives the Binding Update from the wireless communication device (MN) 11 and registers the handover destination IP address as the care-of address (second wireless CoA). Only the packet will be accepted.
  • the HA 23 does not receive a packet during a period from reception of Binding-Update until arrival of a packet from the handover destination, that is, a period of Tdup2 + Tddn2.
  • the alternate long and short dash line indicates the packet flow before the handover.
  • the transmission data 57 that is supposed to be lost due to handover is transmitted to the transmission buffer 57 in the telephone function unit 33.
  • the transmission of data is controlled so as to be transmitted after the handover is completed.
  • FIG. 9 is a diagram for explaining an outline of data transmission processing at the time of handover by the telephone function unit 33.
  • the packet transmitted from the wireless communication device (MN) 11 is lost in the period A corresponding to the lost period Tlost from the time Tws before Tsttlow before the time when the Binding Update is transmitted. For this reason, during this period A, the telephone function unit 33 lowers the encoding bit rate of the transmission data and accumulates a copy thereof in the transmission buffer 57 while transmitting the data.
  • the telephone function unit 33 After that, when transmission of a packet from the handover destination is started, the telephone function unit 33 accumulates new data in the transmission buffer 57 and keeps data in the transmission buffer 57 until the packet in the transmission buffer 57 becomes zero. Is transmitted quickly (period B). Thereafter, the telephone function unit 33 encodes the transmission data at the normal encoding bit rate and stores it in the transmission buffer 57 until the communication is completed or until the period A by the next handover schedule is started. (Period C).
  • FIG. 10 is a flowchart showing the operation at the time of handover by the transmission control unit 56 of the telephone function unit 33.
  • the data transmission process at the time of handover by the telephone function unit 33 will be described in more detail with reference to the flowchart shown in FIG.
  • the handover information acquisition unit 55 of the telephone function unit 33 monitors the handover information from the handover control unit 36 at regular intervals. As a result, when the handover schedule determination information is acquired, the handover preparation time Ts, the handover source uplink absolute delay time Tdup1, the handover destination uplink and downlink absolute delay time Tdup2 are further required handover information from the handover control unit 36. And Tddn2 and handover destination predicted bandwidth Rbup2 are acquired, and the acquired required handover information is supplied to the transmission control unit 56. Thereafter, the handover information acquisition unit 55 monitors the handover schedule notification and the handover completion notification from the handover control unit 36 at regular intervals, supplies the received information to the transmission control unit 56, and acquires the handover completion notification. If so, the process returns to obtaining information on whether or not there is a handover schedule.
  • the transmission control unit 56 When the transmission control unit 56 acquires the handover information from the handover information acquisition unit 55, the transmission control unit 56 transmits, to the communication device 12, handover information excluding information on the handover destination predicted band Rbup2 among the acquired information.
  • the transmission control unit 56 acquires the handover information, first, the data storage start time in the transmission buffer 57, which is the start time Tws of the period A (see FIG. 8) in which the packet loss occurs, and the encoded bit at that time The rate R1 is calculated (step S11).
  • the encoding bit rate R1 is obtained Rbup2 (bps), the reproduction speed VfV (sec / sec) with respect to the standard reproduction speed Vn after the handover of the communication device 12, the maximum capacity Sbf (bit) of the transmission buffer 57, the lost period
  • Tlost (sec) is the standard encoding bit rate Rn (bps), (i) Sbf / Tlost and (ii) Rbup2 / Vf Select the maximum value.
  • the encoding bit rate selected here may be set to a lower encoding bit rate with some margin in consideration of band fluctuations and the like.
  • the reproduction speed Vf after the handover is set in advance as 1.25 times the standard reproduction speed Vn, for example, and is held by both, or notified from the communication apparatus 12 to the wireless communication apparatus 11 in advance.
  • the transmission control unit 56 waits until the packet accumulation start time Tws (step S12).
  • the transmission control unit 56 sets the encoding bit rate of the transmission data to the encoder 44.
  • An instruction is given to lower the calculated encoding bit rate R1 (step S13).
  • the transmission control unit 56 copies the transmission data received from the encoder 44 to the packet transmission unit 45 as it is, and accumulates it in the transmission buffer 57 (step S14).
  • the silence data having a length of a certain length (for example, 500 msec) or more in the transmission data is compressed to the above-mentioned length.
  • step S14 The processing in step S14 is performed until handover completion information is received from the HA 23 (step S15). Thereafter, when handover completion information is received (Yes in S15, start of period B), the transmission control unit 56 transmits the handover completion information to the communication device 12, and transmits the transmission data received from the encoder 44 to the packet transmission unit 45.
  • the data (packet) stored in the transmission buffer 57 is transferred from the oldest to the packet transmission unit 45 at a high speed according to the band and transmitted to the communication device 12 while being stored in the transmission buffer 57 without being passed to (Step S16).
  • the transmission control unit 56 monitors the number of packets in the transmission buffer 57 (step S17). As a result, when the packet in the transmission buffer 57 becomes 0 (Yes in S17, start of period C), the transmission control unit 56 instructs the encoder 44 to restore the encoding bit rate (step S18). The transmission data from the encoder 44 is transferred to the packet transmission unit 45 without being stored in the transmission buffer 57 and transmitted to the communication device 12 (step S19).
  • FIG. 11 is a diagram illustrating a state of a transmission / reception packet with the communication device 12 when the wireless communication device 11 according to the present embodiment performs transmission control at the time of handover.
  • FIG. 12 is a diagram illustrating a state of transmission / reception packets between the wireless communication apparatus and the communication apparatus 12 when the above transmission control is not performed at the time of handover for comparison with FIG. 11 and 12, (a) to (c) respectively indicate the received packet sequence number, the number of received packets per unit time, and the received data amount (byte) per unit time in the communication device 12, and (d) The encoding bit rate (bps) of the transmission data by the radio
  • wireless communication apparatus 11 is shown.
  • the radio communication apparatus (MN) 11 As is clear from the comparison between FIG. 11 and FIG. 12, the radio communication apparatus (MN) 11 according to the present embodiment accumulates transmission packets that will be lost at the time of handover on the radio communication apparatus 11 side and accumulates the transmission packets. Since the transmitted packet is transmitted after the handover, the lost packet that occurred in FIG. 12A does not occur in FIG. Therefore, the continuity of the text can be maintained on the communication device (CN) 12 side even at the time of handover, so that the user who listens to the voice does not feel uncomfortable.
  • the encoding bit rate of transmission data is constant, but the wireless communication apparatus (MN) 11 according to the present embodiment accumulates packets as shown in FIG. 11 (d). During this time, the encoding bit rate is reduced. Therefore, thereafter, the accumulated packets can be transmitted more than usual without causing stagnation in a limited band. As a result, the receiving side communication device (CN) 12 reproduces packets received more than usual shown in FIGS. 11B and 11C at a higher speed than usual, thereby achieving the original absolute delay. Can return to playback. In addition, the wireless communication apparatus (MN) 11 can silently compress the stored packets, thereby reducing the overall data capacity and transmitting the stored packets faster.
  • FIG. 13 is a functional block diagram showing a schematic configuration of the communication device (CN) 12.
  • the communication device 12 includes a network I / F (interface) 81 that connects to the Internet 18 via an Internet service provider (not shown), a communication processing unit 82 that controls connection to the network, and a telephone function unit that executes VoIP applications. 83.
  • the communication processing unit 82 controls the connection of the network I / F 81 to the Internet 18 and executes communication between the telephone function unit 83 and the wireless communication device 11.
  • FIG. 14 is a functional block diagram showing a schematic configuration of the telephone function unit 83 of the communication device 12 shown in FIG.
  • the telephone function unit 83 includes, for example, a soft phone, and has a button input unit 101, a screen display unit 102, a microphone 103, an encoder 104, a packet transmission unit 105, a packet reception unit 106, a jitter buffer, as in the configuration of a known soft phone. 107, a decoder 108, a speaker 109, a jitter buffer monitoring unit 110, a jitter buffer control unit 111, a SIP control unit 112, and an overall control unit 113 that controls the overall operation.
  • the microphone 103 and the speaker 109 are constituted by, for example, a handset 12a as shown in FIG.
  • the overall control unit 113 acquires user operation information via the button input unit 101 and the screen display unit 102, and controls the overall operation based on the acquired information.
  • the SIP control unit 112 also controls SIP procedures for starting and ending a call.
  • the audio data acquired from the microphone 103 is encoded by the encoder 104, and the encoded data is put into a packet from the packet transmission unit 105 and wirelessly transmitted through the communication processing unit 82 and the network I / F 81. It is transmitted to the communication device 11.
  • a packet from the wireless communication apparatus 11 received by the packet receiving unit 106 via the communication processing unit 82 is once taken into the jitter buffer 107 and then read out.
  • the read packet is loaded into the payload by the decoder 108.
  • the portion is decoded and output as reproduced sound from the speaker 109.
  • the reception status of packets in the jitter buffer 107 and the number of packets (data amount) in the jitter buffer 107 are monitored by the jitter buffer monitoring unit 110, and based on the monitoring result, the jitter buffer control unit 111 Processing such as a packet reading speed from the jitter buffer 107 and discarding of the received packet is controlled.
  • the handover information acquisition unit 115 monitors the handover information from the wireless communication apparatus 11 transferred from the HA 23 at regular intervals. As a result, when there is handover schedule determination information, the handover information acquisition unit 115 further acquires the required handover information from the radio communication apparatus 11 and uses the acquired required handover information as the reproduction speed calculation unit 116. To supply.
  • the reproduction speed calculation unit 116 reads the packet reading speed of the jitter buffer 107, that is, the received packet.
  • the playback speed (here, the playback speed of the VoIP application) is calculated, and the calculation result is supplied to the jitter buffer control unit 111.
  • the jitter buffer control unit 111 controls reading of the received packet from the jitter buffer 107 so that the playback speed of the received packet becomes the playback speed calculated by the playback speed calculation unit 116.
  • FIG. 15 is a sequence diagram showing the operation of the main part of the telephone function unit 83.
  • FIG. 16 is a sequence diagram showing a flow of handover information between the wireless communication device (MN) 11, the HA 23 and the communication device (CN) 12.
  • MN wireless communication device
  • CN communication device
  • the alternate long and short dash line indicates the flow of packets before handover from the wireless communication apparatus 11 to the HA 23.
  • the handover information acquisition unit 115 of the telephone function unit 83 monitors the handover information from the wireless communication apparatus 11 at regular intervals. As a result, when the handover schedule determination information is acquired, the handover preparation time Ts, the handover source upstream absolute delay time Tdup1, the handover destination upstream and downstream absolute delay times Tdup2 and Tddn2 from the wireless communication apparatus 11 are further acquired. And supplied to the reproduction speed calculation unit 116.
  • the playback speed calculation unit 116 acquires the current accumulated packet count Tc (sec) in the jitter buffer 107 from the jitter buffer monitoring unit 110, and also acquires the absolute delay time Tdhc3 to HA23.
  • the absolute delay time Tdhc3 to the HA 23 is set to 1 ⁇ 2 of the measured value by measuring the RTT (Round Trip Time) by transmitting / receiving a packet to / from the HA 23.
  • the playback speed calculation unit 116 calculates the playback speed Vs (sec / sec) until the completion of the handover, that is, the time ratio with respect to the standard playback speed Vn based on the obtained information by the following formula.
  • the reproduction speed Vs calculated by the reproduction speed calculation unit 116 is supplied to the jitter buffer control unit 111.
  • the jitter buffer control unit 111 controls reading of the received packet from the jitter buffer 47 so as to reproduce the received packet at the calculated reproduction speed Vs lower than the standard reproduction speed Vn.
  • the playback speed calculation unit 116 controls reading of the received packet from the jitter buffer 107 via the jitter buffer control unit 111 according to the flowchart shown in FIG.
  • the playback speed calculation unit 116 when receiving the handover completion information, the playback speed calculation unit 116 periodically acquires the packet accumulation amount (number of packets) and the packet reception interval (reception speed) in the jitter buffer 107 from the jitter buffer control unit 111. (Step S21), it is monitored whether or not the packet accumulation amount in the jitter buffer 107 exceeds the standard accumulation amount (Step S22). As a result, when the standard accumulation amount is exceeded (Yes in S22), the playback speed control unit 116 calculates the average reception speed in a past fixed period (step S23), and the calculated reception speed is preset. It is determined whether or not 125% of the standard speed corresponding to the reproduction speed Vf (1.25) is exceeded (step S24).
  • the reproduction speed calculation unit 116 instructs the jitter buffer control unit 111 to start high-speed reproduction at the reproduction speed Vf (Step S24).
  • the reproduction speed calculation unit 116 instructs the jitter buffer control unit 111 to start high-speed reproduction at the reproduction speed Vf (Step S24).
  • step S27 determines whether or not the reception speed is the standard speed (100%). As a result, if the standard speed is exceeded (Yes in S27), the playback speed calculation unit 116 starts high-speed playback at the same speed as the reception speed calculated in step S23 with respect to the jitter buffer control unit 111. Instructed (step S28), the process proceeds to step S26.
  • the reproduction speed calculation unit 116 continues to regularly monitor the accumulation amount of the jitter buffer 107 and the packet reception interval (reception speed) thereafter.
  • step S26 when the packet accumulation amount in the jitter buffer 107 becomes standard (Yes in S26), it is determined whether or not the average packet reception interval (reception speed) is within a certain range from the standard value (step S29). ). As a result, when the packet accumulation amount is standard and the packet reception interval is within a certain range (Yes in S29), the jitter buffer control unit 111 is instructed to return the jitter buffer 107 to normal control (step S30). Then, the control at the time of handover is terminated. If the average reception speed calculated in step S23 does not exceed the standard speed in step S27 (No in S27), the process proceeds to step S30 and similarly returns the jitter buffer 107 to normal control. .
  • FIG. 18 is a diagram for explaining packet reproduction control by the communication device 12 described above.
  • 18A shows the number of packets received by the jitter buffer 107 per unit time
  • FIG. 18B shows the amount of packets stored in the jitter buffer 107
  • FIG. 18C shows the playback speed.
  • the jitter buffer 107 receives the number of packets larger than 125% of the standard number of received packets, and thereafter In this example, the number of packets equal to the standard number of received packets is received.
  • the packet accumulation amount Tn indicates a standard accumulation amount corresponding to the standard reproduction speed Vn.
  • the communication device 12 determines the application reproduction speed from the standard reproduction speed Vn based on the handover information including the handover schedule notification, in the jitter buffer 107 at the reception start time of the packet from the handover destination. Is reduced to a constant reproduction speed Vs at which the number of packets becomes zero. After that, it is confirmed that the handover is completed and the packet accumulation amount and the packet reception interval in the jitter buffer 107 have returned to the standard, and the standard reproduction speed Vn is restored.
  • the application can be played back at a constant playback speed that is closer to the standard playback speed, so that the playback quality and real-time performance are not degraded. .
  • the packet playback speed control at the playback speed Vs lower than the standard playback speed Vn by the jitter buffer controller 111 is, for example, the first playback speed control method or the second playback speed control method described below. Execute by either.
  • First playback speed control method TR1 is the packet reading interval from the jitter buffer 107 with respect to the standard playback speed Vn, (Tb + Tc) / (Tb + Ta) is k, and the jitter corresponding to the calculated playback speed Vs.
  • TR TR1 / k.
  • the [ ⁇ Vn / (Vn-Vs) ⁇ -1] -th read packet is copied and stored in the memory in the decoder 108, and the copy source packet is stored. After reproduction, the copied packet is read and reproduced at the next reproduction timing.
  • the playback speed Vs is set to 80% of the standard playback speed Vn, as shown in FIG. 19, the sequential four packets P1 to P4 in the jitter buffer 107 are sequentially read and played back, The fourth packet P4 is copied, and the copied packet P4 ′ is reproduced at the next reproduction timing after reproducing the copy source packet P4.
  • the TD is increased by the reproduction interval time by copying. If the [ ⁇ Vn / (Vn ⁇ Vs) ⁇ ⁇ 1] -th packet to be read has not arrived or has been discarded and is not in the jitter buffer 107, the packet at the next reproduction timing is The same processing is performed.
  • the communication device 12 appropriately responds to a state in which a period in which packets do not arrive occurs at the time of handover of the wireless communication device 11, and then the accumulated packets arrive from the wireless communication device 11 at high speed. Thus, packets can be played back at an optimum speed.
  • the case where a packet is transmitted from the wireless communication apparatus 11 to the communication apparatus 12 via the HA 23 using mobile IP reverse tunneling or NEMO is exemplified.
  • Lost of the transmission packet from the device 11 to the communication device 12 optimizes the route with Mobile IPv6, and also when the packet is directly transmitted and received between the wireless communication device 11 and the communication device 12, This also occurs due to the difference in delay time. Accordingly, even in such a case, the packet loss can be prevented by accumulating the packets transmitted by the wireless communication apparatus 11 at the time of handover and transmitting the accumulated packets after the handover in the same manner as in the above embodiment. it can.
  • the transmission packets in this period may be stored in the transmission buffer 57 and transmitted at high speed after the handover is completed.
  • the period during which the HA 23 does not receive a packet from the wireless communication apparatus 11 due to handover is Tdup2 + Tddn2.
  • the reproduction speed calculation unit 116 calculates the reproduction speed Vs
  • the number of packets in the jitter buffer 107 is zero at the start of packet reception from the handover destination.
  • the playback speed Vs can also be calculated so that the number of packets in the jitter buffer 107 becomes a predetermined number at the start of reception of packets from the handover destination.
  • FIG. 20 is a diagram showing a schematic configuration of a communication network that can be used by the communication apparatus according to the second embodiment of the present invention.
  • the communication network shown in FIG. 20 has the same configuration as that in FIG.
  • the wireless communication device (MN) 121 that is a mobile node can be handed over between the first wireless communication network 15 and the second wireless communication network 16, and the communication device (CN) 122 that is the opposite node , VoIP, which is a real-time communication system application, is assumed to make a call.
  • the same reference numerals are assigned to the same components as those in the communication network shown in FIG.
  • the communication device 122 is composed of, for example, a personal computer to which a handset 122a is connected and a soft phone as a telephone function unit is installed, and is connected to the Internet 18 as a communication network through an Internet service provider (not shown).
  • the wireless communication device 121 registers the IP address of the first wireless communication network 15 in the HA 23 as a care-of address (first wireless CoA), and communicates with the communication device 122 via the first wireless communication network 15. It is assumed that handover is performed from the current state to the second wireless communication network 16.
  • FIG. 21 is a functional block diagram showing a schematic configuration of the wireless communication apparatus 121 shown in FIG. Similarly to the wireless communication device 11 illustrated in FIG. 2, the wireless communication device 121 includes a first wireless I / F (interface) 131 corresponding to the first wireless communication network 15 and a second wireless communication network 16 corresponding to the second wireless communication network 16.
  • a wireless information acquisition unit 135 that acquires wireless information of the second wireless communication network 16, and a handover control unit 136 that controls a handover between the first wireless communication network 15 and the second wireless communication network 16.
  • the communication processing unit 134 makes a call between the telephone function unit 133 and the communication device 122 via the first wireless communication network 15 or the second wireless communication network 16.
  • the connection of the first wireless I / F 131 or the second wireless I / F 132 is controlled so as to communicate with the HA 23 under the control of the handover control unit 136.
  • the wireless information acquisition unit 135 receives the first wireless communication network 15 and the corresponding wireless information from the first wireless I / F 131 and the second wireless I / F 132 as wireless information.
  • the communication quality (for example, RSSI) of the second wireless communication network 16 is acquired, and the acquired communication quality is supplied to the handover control unit 136.
  • the handover control unit 136 Based on the communication quality from the radio information acquisition unit 135, the handover control unit 136 generates handover information including a decision whether to schedule a handover, that is, whether to start preparation for handover, and the handover information Based on the above, handover is controlled.
  • the handover control unit 136 for example, in the same way as the handover control unit 36 shown in FIG. 2, the communication quality acquired from the first wireless I / F 131 and the second wireless I / F 132 via the wireless information acquisition unit 135, respectively. Based on the above, the handover schedule is determined.
  • Up and down absolute delay times Tdup2 (sec) and Tddn2 (sec) between the radio communication apparatus 121 and the HA 23 in the handover destination radio communication network (here, the second radio communication network 16), and the handover of the HA 23 is completed.
  • the handover destination information when the handover request information arrives at the HA 23 And acquires the calculated bandwidth Rbdn2 (bps) of the downlink on line communication network.
  • the handover control unit 136 supplies the acquired information as necessary handover information to the telephone function unit 133 including handover schedule determination information indicating schedule determination of handover.
  • the telephone function unit 133 selectively transmits the handover information acquired from the handover control unit 136 to the communication device 12 via the HA 23 as a handover advance notice message according to the comparison result of absolute delay time described later.
  • the handover preparation time Ts, handover source uplink and downlink absolute delay times Tdup1 and Tddn1, handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, and handover destination predicted bandwidth Rbdn2 by the handover control unit 36 are, for example, Each is acquired by the acquisition method described in the first embodiment.
  • the handover preparation time Ts is acquired by the acquisition method described with reference to FIGS. 4 (a) and 4 (b).
  • the absolute delay times Tdup1, Tddn1, Tdup2, and Tddn2 are acquired by any one of the first to third absolute delay time acquisition methods, and are stored in a memory (not shown) in the handover control unit 136 for each radio communication network. ).
  • the reception time of the measurement packet from the HA 23 received via the first wireless I / F 131 and the second wireless I / F 132, and the time of the measurement packet From the stamp the absolute delay times Tdup1, Tddn1, Tdup2, and Tddn2 of the corresponding network are measured.
  • the absolute delay times Tdup1, Tdup2, and Tddn2 are acquired by the above [Equation 2] and [Equation 3], and the absolute delay time Tddn1 is obtained by the following equation. get.
  • the downlink predicted bandwidth Rbdn2 of the handover destination is obtained by predicting the downlink radio state in the handover destination radio communication network when the handover of the HA 23 is completed.
  • the handover control unit 136 stores, for example, a conversion table between the radio state (communication quality) and the throughput (predicted bandwidth) as shown in FIG.
  • the handover control unit 36 linearly predicts the handover destination radio status at the completion of the handover based on the handover destination radio status at the time when the handover schedule is determined and the handover destination radio status a predetermined time before that time. Then, based on the predicted radio state, the handover destination predicted bandwidth Rbdn2 at the time of handover completion is acquired from the conversion table of FIG.
  • the handover completion time is determined from the handover schedule determination time to the handover preparation time Ts and the uplink between the HA 23 and the radio communication device 11 in the handover destination radio communication network (here, the second radio communication network 16).
  • the absolute delay time Trup2 is added.
  • the handover control unit 136 sets the handover preparation time Ts, the handover source uplink and downlink absolute delay times Tdup1 and Tddn1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, and the handover destination downlink predicted bandwidth Rbdn2.
  • the acquired information is supplied to the telephone function unit 133 as required handover information together with handover schedule determination information indicating handover schedule determination.
  • the handover control unit 136 determines a handover schedule, the handover control unit 136 executes a handover process.
  • FIG. 22 is a sequence diagram for explaining a handover process between the wireless communication apparatus 121 and the HA 23.
  • the handover control unit 136 of the wireless communication apparatus (MN) 121 determines a handover schedule
  • the handover control unit 136 controls the communication processing unit 134 to transfer the second wireless I / F 132 to the second wireless communication network 16. Connecting. Thereafter, when the handover preparation time Ts elapses, the handover control unit 136 transmits a Registration request (handling update in NEMO) to the HA 23 via the second wireless communication network 16 that is the handover destination.
  • a Registration request (handling update in NEMO)
  • the HA 23 Upon receipt of the handover request information, the HA 23 registers the IP address of the handover destination as a care-of address (second wireless CoA), and registers Registration Reply (Binding Acknowledge in NEMO) as the second wireless communication network. 16 to the wireless communication apparatus 121 via Note that the HA 23 registers only one care-of address with the wireless communication apparatus 121. Therefore, the care-of address of the handover destination (second radio CoA) is registered by overwriting the care-of address of the handover source (first radio CoA) already registered.
  • the handover control unit 136 starts transmission / reception of a packet by the second wireless communication network 16 at the handover destination and performs communication.
  • the processing unit 134 is controlled to disconnect the connection between the first wireless I / F 31 and the first wireless communication network 15 that is the handover source.
  • the handover control unit 136 transmits a handover completion notification indicating that to the telephone function unit 133 as the handover information.
  • the wireless communication device (MN) 121 receives the packet transferred from the HA 23 to the first wireless communication network 15 of the handover source after disconnecting the first wireless I / F 131 of the handover source from the first wireless communication network 15. It becomes impossible and the lost packet occurs.
  • FIG. 23 is a diagram for explaining the occurrence of packet loss in this case.
  • NEMO will be described as an example.
  • Tddn1 of the handover source downlink is longer than the absolute delay time Tddn2 of the handover destination downlink, (Tddn1-Tddn2) from the time when the wireless communication device (MN) 121 receives BindingckAck.
  • the packet transmitted from the first wireless communication network 15 that is the handover source in the previous period cannot be received by the wireless communication apparatus (MN) 121, and this period (Tddn1-Tddn2) becomes the lost period Tlost of the packet.
  • the communication device (CN) 122 assumes that the transmission timing of the data Dat (n1) transmitted first in the lost period Tlost is T1, and the transmission timing of the data Dat (n2) transmitted last is T2.
  • CN) 122 receives a handover notice message Msg (HO) from the wireless communication apparatus (MN) 121 via HA 23, and until a transmission timing T1 of data Dat (n1), Tlowstt (sec) is a handover notice.
  • the absolute delay time Tdn with the HA 23 can be obtained by transmitting / receiving a packet to / from the HA 23, measuring RTT (Round Trip Time), and halving the measured value.
  • the telephone function unit 133 When the telephone function unit 133 obtains the handover information from the handover control unit 136, it compares the downlink absolute delay times Tddn1 and Tddn2 of the handover source and the handover destination, and if Tddn1> Tddn2, A handover notice message is transmitted to the communication device (CN) 122 via the HA 23.
  • the communication device (CN) 122 based on the handover information from the wireless communication device (MN) 121 and the absolute delay time Tdn with the HA 23 described above, the transmission data that is supposed to be lost due to the handover is Data is stored in the communication device (CN) 122 and data transmission is controlled so that the wireless communication device 121 can receive the data after the handover is completed.
  • the absolute delay time Tdn with the HA 23 may be measured in advance and stored in the communication device (CN) 122, or measured by receiving handover information from the wireless communication device (MN) 121. You may make it do.
  • FIG. 24 is a functional block diagram showing a schematic configuration of the communication device (CN) 122.
  • the communication device 122 includes a network I / F (interface) 181 that connects to the Internet 18 via an Internet service provider (not shown), a communication processing unit 182 that controls connection to the network, and a telephone function unit that executes VoIP applications. 183.
  • the communication processing unit 182 controls the connection of the network I / F 181 to the Internet 18 and executes communication between the telephone function unit 183 and the wireless communication device 121. Therefore, the network I / F 181 and the communication processing unit 182 constitute a communication unit.
  • FIG. 25 is a functional block diagram showing a schematic configuration of the telephone function unit 183 of the communication device 122 shown in FIG.
  • the telephone function unit 183 includes, for example, a soft phone, and has a configuration of a known soft phone, like the communication device 12 illustrated in FIG. 14, and includes a button input unit 141, a screen display unit 142, a microphone 143, an encoder 144, a packet The transmitter 145, the packet receiver 146, the jitter buffer 147, the decoder 148, the speaker 149, the jitter buffer monitor 150, the jitter buffer controller 151, the SIP controller 152, and the overall controller 153 that controls the overall operation.
  • the microphone 143 and the speaker 149 are configured by a handset 122a as shown in FIG. 20, for example.
  • the overall control unit 153 acquires user operation information via the button input unit 141 and the screen display unit 142, and controls the overall operation based on the acquired information.
  • the SIP control unit 152 controls SIP procedures for starting and ending a call.
  • the audio data acquired from the microphone 143 is encoded by the encoder 144 which is an encoding unit, and the encoded data is put into a packet from the packet transmission unit 145, and the communication processing unit 182 and the network I
  • the data is transmitted to the wireless communication apparatus 121 via / F181.
  • a packet from the wireless communication apparatus 121 received by the packet receiving unit 146 via the communication processing unit 182 is once taken into the jitter buffer 147 and read out.
  • the read packet is loaded into the payload by the decoder 148.
  • the portion is decoded and output as reproduced sound from the speaker 149.
  • the reception status of packets in the jitter buffer 147 and the number of packets (data amount) in the jitter buffer 147 are monitored by the jitter buffer monitoring unit 150. Based on the monitoring result, the jitter buffer control unit 51 Processing such as a packet reading speed from the jitter buffer 47 and discarding of the received packet is controlled.
  • the telephone function unit 183 has the same configuration as the telephone function unit 33 of the wireless communication apparatus 11 according to the first embodiment shown in FIG.
  • the handover information acquisition unit 155 monitors handover notification messages from the wireless communication apparatus 121 at regular intervals, and acquires handover schedule determination information for determining a handover schedule. When the handover schedule determination information is acquired, the handover information acquisition unit 155 further acquires the required handover information from the radio communication apparatus 121 and supplies the acquired required handover information to the transmission control unit 156. .
  • the transmission control unit 156 controls the encoding bit rate of transmission data by the encoder 144 and the transmission of data from the encoder 144 to the packet transmission unit 145. That is, the transmission control unit 156 directly transmits the data encoded by the encoder 44 to the packet transmission unit 145 in a normal call state in which handover information is not supplied from the handover information acquisition unit 155. On the other hand, when handover information is supplied from the handover information acquisition unit 155, the transmission control unit 156 acquires the absolute delay time Tdn and performs handover based on the absolute delay time Tdn and the handover information. Is stored in the transmission buffer 157, and the stored data is controlled to be transmitted to the packet transmission unit 145 after the handover is completed. The transmission control by the transmission control unit 156 will be described later.
  • telephone function unit 183 constitutes an execution unit that executes a real-time communication system application and a control unit that controls transmission of data of the application.
  • FIG. 26 is a diagram for explaining an outline of data transmission processing at the time of handover by the telephone function unit 183.
  • the packet transmitted from the communication device (CN) 122 is the lost period Tlost in which the period Tlowstt (sec) has elapsed from the time when the handover notice message Msg (HO) is received from the wireless communication device (MN) 121. Lost in (period A). For this reason, during this period A, the telephone function unit 183 lowers the encoding bit rate of the transmission data and accumulates a copy thereof in the transmission buffer 157 while transmitting the data.
  • the telephone function unit 183 stores the data in the transmission buffer 157 until the packet in the transmission buffer 157 reaches 0 while accumulating new data in the transmission buffer 157. Is transmitted quickly (period B). Thereafter, the telephone function unit 183 encodes the transmission data at the normal encoding bit rate and stores it in the transmission buffer 157 until the communication is completed or until the period A by the next handover schedule is started. (Period C).
  • FIG. 27 is a flowchart showing the operation at the time of handover by the transmission control unit 156 of the telephone function unit 183.
  • the data transmission processing at the time of handover by the telephone function unit 183 will be described in more detail with reference to the flowchart shown in FIG.
  • the handover information acquisition unit 155 of the telephone function unit 183 monitors the handover information from the wireless communication device (MN) 121 transferred from the HA 23 at regular intervals.
  • the required handover information is the handover preparation time Ts, the handover source uplink absolute delay times Tdup1 and Tddn1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, the handover destination predicted bandwidth Rbdn2 Is acquired (step S111), and the acquired required handover information is supplied to the transmission control unit 156.
  • the transmission control unit 156 acquires the handover information, first, the time Tlowstt from the time when the handover notice message Msg (HO) is received to the period A in which packet loss occurs (see FIG. 26), the lost period Tlost of the packet that is the period A And the encoding bit rate R1 are calculated (step S112).
  • the time Tlowstt is calculated based on the equation shown in Equation 4 above, and the lost period Tlost is calculated from (Tddn1-Tddn2).
  • the encoding bit rate R1 is obtained Rbdn2 (bps)
  • the reproduction speed Vf sec / sec
  • the maximum capacity Sbf (bit) of the transmission buffer 157 the maximum capacity of the transmission buffer 157 .
  • Lost period Tlost sec
  • standard encoding bit rate Rn bps
  • Sbf / Tlost Sbf / Tlost
  • Rbdn2 / Vf Select the maximum bit rate.
  • the encoding bit rate selected here may be set to a lower encoding bit rate with some margin in consideration of band fluctuations and the like.
  • the reproduction speed Vf after the handover is set in advance as, for example, 1.25 times the standard reproduction speed Vn and is held by both, or notified from the communication apparatus 122 to the wireless communication apparatus 121 in advance.
  • the transmission control unit 156 waits for the Tlowstt time (step S113), and when the Tlowstt time has elapsed (start of the lost period Tlost), the encoding bit rate obtained by calculating the encoding bit rate of the transmission data to the encoder 144.
  • the transmission data received from the encoder 144 is transferred to the packet transmission unit 145 as it is, and the transmission data is copied and stored in the transmission buffer 157 (step S114).
  • the silence data having a length of a certain length (for example, 500 msec) or more in the transmission data is compressed to the above-mentioned length.
  • step S114 The process of step S114 is performed until the lost period Tlost ends (step S115).
  • the transmission control unit 156 transmits the transmission received from the encoder 144. While storing the data in the transmission buffer 157 without passing the data to the packet transmission unit 145, the data (packets) stored in the transmission buffer 157 is transferred from the oldest to the packet transmission unit 145 at a high speed according to the bandwidth. It transmits to the radio
  • MN wireless communication apparatus
  • the transmission control unit 156 monitors the number of packets in the transmission buffer 157 (step S117). As a result, when the packet in the transmission buffer 157 becomes 0 (Yes in S117, the start of period C), the transmission control unit 156 instructs the encoder 144 to restore the encoding bit rate (step S118). The transmission data from the encoder 144 is transferred to the packet transmission unit 145 without being stored in the transmission buffer 157 and transmitted to the wireless communication device (MN) 121 (step S119).
  • MN wireless communication device
  • FIG. 28 is a diagram illustrating a state of a received packet in the wireless communication device when transmission control is performed at the time of handover by the communication device 122 according to the present embodiment.
  • FIG. 29 is a diagram illustrating a state of a received packet in the wireless communication apparatus when the above transmission control is not performed at the time of handover. 28 and 29, (a) shows the sequence number of the received packet, (b) shows the number of received packets per unit time, and (c) shows the received data amount (byte) per unit time.
  • the communication device (CN) 122 As is clear from the comparison between FIG. 28 and FIG. 29, the communication device (CN) 122 according to the present embodiment accumulates in the transmission buffer 157 packets that the wireless communication device (MN) 121 will lose at the time of handover. Then, since the accumulated packets are transmitted so that the wireless communication apparatus (MN) 121 can receive them after handover, the lost packets that occurred in FIG. 29A do not occur in FIG. Therefore, even at the time of handover, the continuity of the text can be maintained on the wireless communication device (MN) 121 side that is the communication partner, so that the user who listens to the voice does not feel uncomfortable.
  • the communication device (CN) 122 since the communication device (CN) 122 according to the present embodiment reduces the encoding bit rate by the encoder 144 while accumulating lost packets, the accumulated packets are limited thereafter. It is possible to transmit more than usual without causing retention in the band. Therefore, the receiving-side wireless communication device (MN) 121 reproduces packets received more than usual shown in FIGS. 28 (b) and (c) at a higher speed than usual, thereby achieving the original absolute delay. Can return to playback. Further, by silently compressing the packet stored in the transmission buffer 157, the overall data capacity can be reduced, and the stored packet can be transmitted faster.
  • FIG. 30 is a functional block diagram showing a schematic configuration of the telephone function unit 133 of the wireless communication apparatus 121.
  • FIG. 31 is a sequence diagram showing the operation of the main part of the telephone function unit 133.
  • the telephone function unit 133 is made of, for example, a known soft phone, and similarly to the telephone function unit 183 of the communication apparatus 122 shown in FIG.
  • a control unit 213 is included.
  • the overall control unit 213 acquires user operation information via the button input unit 201 and the screen display unit 202, and controls the overall operation based on the acquired information.
  • the SIP control unit 212 also controls SIP procedures for starting and ending a call.
  • the audio data acquired from the microphone 203 is encoded by the encoder 204, and the encoded data is put into a packet from the packet transmission unit 205 and transmitted to the communication device 122 via the communication processing unit 134.
  • the packet from the communication device 122 received by the packet receiving unit 206 via the communication processing unit 134 is once fetched into the jitter buffer 207 and read out. Are decoded and output as reproduced sound from the speaker 209.
  • the jitter buffer monitoring unit 210 monitors the reception status of packets in the jitter buffer 207 and the number of packets (data amount) in the jitter buffer 207. Based on the monitoring result, the jitter buffer monitoring unit 210 The controller 211 controls processing such as the packet reading speed from the jitter buffer 207 and discarding of received packets.
  • the wireless communication apparatus 121 shown in FIG. 20 is further provided with a telephone function unit 133, a handover information acquisition unit 215, and a playback speed calculation unit 216. That is, the telephone function unit 133 has the same configuration as the telephone function unit 83 of the communication device 12 shown in FIG.
  • the handover information acquisition unit 215 monitors the handover information from the handover control unit 136 at regular intervals, and when there is handover information, as described above, the handover source included in the handover information And the absolute delay times Tddn1 and Tddn2 of the downlink of the handover destination are compared, and when Tddn1> Tddn2, the acquired handover information is transmitted to the communication device 122 as a handover notice message.
  • the handover information acquisition unit 215 further monitors the handover completion notification included in the handover information when Tddn1> Tddn2, and when receiving the handover completion notification, the reproduction speed calculation unit 216 is notified. As a result, the playback speed calculation unit 216 notifies the jitter buffer control unit 211 to play back at a predetermined speed Vf that is faster than the standard playback speed Vn (for example, 1.25 times the standard playback speed Vn).
  • the playback speed calculation unit 216 acquires the packet accumulation amount and the packet reception interval in the jitter buffer 207 from the jitter buffer monitoring unit 210 at regular intervals, and the packet reception interval corresponds to the reception interval of the standard playback speed Vn.
  • the packet accumulation amount is equal to or less than the standard packet accumulation amount as described above, the jitter buffer control unit 211 is instructed to return to the normal reproduction control.
  • the handover information acquisition unit 215 does not generate a packet loss due to handover when the absolute delay times Tddn1 and Tddn2 of the handover source and the handover destination included in the acquired handover information are Tddn1 ⁇ Tddn2.
  • the handover notification message is not transmitted to the communication device 122, and even when the handover completion notification is received, the playback speed calculation unit 216 is not notified of this. Therefore, in this case, the jitter buffer control unit 211 reproduces the packet in the jitter buffer 207 by normal control based on the monitoring result by the jitter buffer monitoring unit 210.
  • FIG. 32 is a diagram for explaining packet reproduction control by the wireless communication apparatus 121 described above.
  • FIG. 32A shows the number of packets received by the jitter buffer 207 per unit time
  • FIG. 32B shows jitter.
  • the amount of packets stored in the buffer 207, FIG. 32 (c) shows the playback speed.
  • the communication device 122 accumulates transmission data that is supposed to be lost due to handover, and transmits the data at a high speed at a timing that can be received by the wireless communication device 121 after the handover is completed.
  • the playback speed is set to a speed Vf higher than the standard playback speed Vn. Therefore, the packet accumulation amount in the jitter buffer 207 is unit time. After the number of received packets returns to the standard, it gradually decreases, and when the standard accumulation amount is reached, the playback speed also returns to the standard playback speed Vn.
  • the wireless communication device (MN) 121 determines a handover schedule
  • the wireless communication device (MN) 121 transmits a handover notification message to the communication device (CN) 122 according to the present embodiment.
  • the communication device 122 receives the handover advance notice message from the wireless communication device 121, estimates transmission data that is thought to be lost due to the handover based on the handover information included in the handover advance notice message, and the estimated transmission Data is stored in the transmission buffer 157, and is transmitted to the wireless communication apparatus 121 at a speed matching the wireless band after the handover is completed.
  • the transmission data accumulation start by the transmission buffer 157 is determined by the transmission control unit 156 calculating the transmission data accumulation start timing that is considered to be lost based on the timing of the received handover notice message. For this reason, in order to more accurately estimate and accumulate the packet that seems to be lost, the accumulation start timing calculated by the transmission control unit 156 and the lost timing generated by the handover actually performed by the wireless communication apparatus 11 are set. It is preferable to make them match exactly. As the method, the following two methods can be considered.
  • the accumulation start message is transmitted from the wireless communication apparatus 121 so that the accumulation start message reaches the communication apparatus 122 at the timing when the transmission buffer 157 of the communication apparatus 122 starts the accumulation process.
  • the timing cycle of the communication device 122 is synchronized with the timing cycle of the wireless communication device 121.
  • an accumulation start message is sent from the wireless communication apparatus 121 to the communication apparatus 122 before the transmission delay time from the wireless communication apparatus 121 to the communication apparatus 122 from the accumulation start timing. That's fine. In this way, if handover is performed during the time measurement in the wireless communication apparatus 121, there is no theoretical error.
  • the wireless communication device 121 sends both a prior handover notice message and a previous accumulation start message, and the communication device 122 monitors the stay from the reception state of the packet, When it is determined that no retention has occurred, priority is given to the previous accumulation start message, and when it is determined that retention has occurred, accumulation is performed in accordance with the scheduled accumulation start timing based on the handover notice message. It is preferable to start.
  • the communication device 122 receives the wireless state from the wireless communication device 121 for a certain period, measures the RTP packet reception period in a state where the wireless state is determined to be good, and performs the measurement. It is conceivable to synchronize the timing period of the communication apparatus 122 with the wireless communication apparatus 121 using the received reception period as the correction period. Accordingly, the communication device 122 can start accumulation by correcting the accumulation start timing calculated by the wireless communication device 121.
  • the timing cycle of the communication device 122 is corrected using the RTP packet from the wireless communication device 121, for example, in a VoIP application, basically, an audio RTP packet is transmitted at a constant cycle, and the wireless state is When it is favorable, the jitter is small, so that the timing periods of the wireless communication device 121 and the communication device 122 can be accurately synchronized.
  • the handover schedule is changed on the wireless communication apparatus 121 side, a message to that effect is sent from the wireless communication apparatus 121 to the communication apparatus 122. Then, the operation of the communication device 122 is corrected according to the scheduled change of the handover. For example, if the wireless communication apparatus 121 detects that a stagnation has occurred from a packet that has arrived at the wireless communication apparatus 121 before the handover after sending a handover notification message to the communication apparatus 122, the wireless communication apparatus 121 A message indicating the occurrence of stagnation is sent.
  • the communication apparatus 122 sets an estimated accumulation capacity within a range not exceeding the set maximum accumulation time (the maximum capacity Sbf of the transmission buffer 157). Further increase, and accumulation starts at a timing going back from the initial accumulation start timing. Then, the encoding bit rate is recalculated with the increased accumulation time.
  • the accumulation time Tlost is set to 200 (msec). Is set.
  • the maximum capacity Sbf of the transmission buffer 157 is set to 500 (msec)
  • the amount is increased by 300 (msec) with respect to the previous accumulation start timing T1 so that the accumulation time becomes 500 (msec).
  • Accumulation starts at the timing of (T1-300) (msec) retroactive.
  • the packet when packet retention occurs on the wireless route near the handover, the packet is accumulated including the remaining amount, and the accumulated packet is transmitted using the handover destination route.
  • the non-transmission state (gap) itself due to the retention of the handover source cannot be compensated for, but the number of lost packets during that time can be reduced.
  • a playback speed calculation unit 216 included in the telephone function unit 133 of the wireless communication apparatus 121 shown in FIG. 30 is added to the telephone function unit 33 of the wireless communication apparatus 11 according to the first embodiment, and at the time of handover.
  • a wireless communication apparatus that performs both the transmission control and the reproduction control described above can be configured.
  • a playback speed calculation unit 116 included in the telephone function unit 83 of the communication apparatus 12 illustrated in FIG. 14 is added to the telephone function unit 183 of the communication apparatus 122 according to the second embodiment, and the above-described operation is performed at the time of handover. It is possible to configure a communication device that performs both transmission control and reproduction control.
  • the present invention is not limited to the case of executing a VoIP application, but can be effectively applied to the case of executing a real-time communication application such as streaming transmission of multimedia data such as video and music.
  • the application execution unit may be configured by a multimedia function unit having a similar transmission control function instead of the telephone function unit.
  • the present invention is not limited to handover between cdma2000 1xEV-DO and a wireless LAN, but other wireless communication networks such as PDC (Personal Digital Cellular), W-CDMA (Wideband) CDMA), PHS (Personal Handy-
  • PDC Personal Digital Cellular
  • W-CDMA Wideband
  • PHS Personal Handy-
  • the present invention can be effectively applied to handover between any different wireless communication networks such as phone (System), Bluetooth, WiMAX, LTE (Long Term Evolution), UMB (Ultra Mobile Broadband), and IMT-Advanced.

Abstract

When the start of preparation of a handover from a first wireless communication network (15) to a second wireless communication network (16) is determined at the time of a handover from the first wireless communication network (15) to the second wireless communication network (16), data is transmitted through the first wireless communication network (15) and stored for a predetermined time, and the stored data is transmitted through the second wireless communication network (16) following the handover. Consequently, it becomes possible that the data during a predetermined time that might otherwise be lost by handover is stored while being transmitted, and the stored data is transmitted after the handover. The data can thereby be handed over to a different wireless communication network without causing packet loss, and a wireless communication device and a communication device which can always maintain stabilized reproduction quality and real-time performance are provided.

Description

無線通信装置および通信装置Wireless communication device and communication device 関連出願の相互参照Cross-reference of related applications
　本出願は、２００８年３月２７日に出願された日本国特許出願２００８－８４１２４号および同２００８－８４１３１号の優先権を主張するものであり、これら先の出願の開示全体をここに参照のために取り込む。 This application claims the priority of Japanese Patent Applications Nos. 2008-84124 and 2008-84131 filed on Mar. 27, 2008, the entire disclosures of which are hereby incorporated herein by reference. For capture.
　本発明は、異なる無線通信ネットワーク間でのハンドオーバが可能な無線通信装置、および、該無線通信装置と通信する通信装置に関するものである。 The present invention relates to a wireless communication apparatus capable of performing handover between different wireless communication networks, and a communication apparatus communicating with the wireless communication apparatus.
　近年、ＩＥＴＦ（Internet Engineering Task Force）では、ユビキタス環境の実現に向けて、例えば携帯電話ネットワークや無線ＬＡＮ等、異なる複数の無線通信ネットワーク間でのハンドオーバを可能とするＩＰモビリティ技術が検討されている（例えば、非特許文献１参照）。このＩＰモビリティ技術における具体的なプロトコルとしては、通信端末個々の移動をサポートするモバイルＩＰｖ４およびモバイルＩＰｖ６（以下、これらを総称してモバイルＩＰと略称する）が知られており、ネットワーク単位での移動をサポートするＮＥＭＯ（Network Mobility）が知られている。 In recent years, IETF (Internet Engineering Task Force) has been studying IP mobility technology that enables handover between different wireless communication networks, such as mobile phone networks and wireless LANs, in order to realize a ubiquitous environment. (For example, refer nonpatent literature 1). As specific protocols in this IP mobility technology, Mobile IPv4 and Mobile IPv6 (hereinafter collectively referred to as mobile IP) supporting movement of individual communication terminals are known, and movement in units of networks is known. NEMO (Network Mobility) that supports the network is known.
　モバイルＩＰやＮＥＭＯでは、移動ノード（ＭＮ：Mobile Node）がハンドオーバする際、当該ＭＮが属するホームエージェント（ＨＡ：Home Agent）に、ハンドオーバ先の無線通信ネットワークのＩＰアドレスを気付けアドレス（ＣｏＡ：Care of Address）として登録することにより、ハンドオーバ先の無線通信ネットワークを介して、通信相手である対向ノード（ＣＮ：Correspondent Node）との通信を可能としている。 In mobile IP or NEMO, when a mobile node (MN: Mobile Node) performs handover, the home agent (HA: Home Agent) to which the MN belongs is assigned the care-of address (CoA: Care of) of the wireless communication network of the handover destination. By registering as (Address), communication with a counterpart node (CN: Correspondent Node) which is a communication partner is enabled via the wireless communication network of the handover destination.
　ここで、ハンドオーバ方式には、ハンドオーバ元のネットワークを切断する前にハンドオーバ先のネットワークを接続するＭＢＢ（Make-Before-Break）方式や、ハンドオーバ元のネットワークを切断してからハンドオーバ先のネットワークを接続するＢＢＭ（Break-Before- Make）方式等が知られている。ＭＢＢ方式は、ＭＮを無線通信ネットワークにシームレスに切り替え接続するので、ＶｏＩＰなどのリアルタイム性を有するアプリケーションには有効である。 Here, as a handover method, an MBB (Make-Before-Break) method in which a handover destination network is connected before disconnecting the handover source network, or a handover destination network is connected after disconnecting the handover source network. A BBM (Break-Before- Make) method is known. Since the MBB system seamlessly switches and connects the MN to the wireless communication network, it is effective for applications having real-time properties such as VoIP.
　しかし、ＭＢＢ方式によりハンドオーバを行う場合、ＨＡは、ＭＮからのハンドオーバ要求情報であるRegistration Request（ＮＥＭＯでは、Binding Update）を受信して、ハンドオーバ先のＣｏＡを登録することにより、以後は、ハンドオーバ先の無線通信ネットワークを介して、ＭＮとＣＮとの間で通信が行われることになる。また、ＭＮは、ＨＡから返信されるハンドオーバ完了情報であるRegistration Reply（ＮＥＭＯでは、Binding Acknowledge）を受信して、ハンドオーバ元の無線通信ネットワークとの接続を切断することにより、以後は、ハンドオーバ先の無線通信ネットワークを介して通信を行うことになる。 However, when performing handover by the MBB method, the HA receives Registration Request (Binding Update in NEMO) that is handover request information from the MN, and registers the handover destination CoA. Communication is performed between the MN and the CN via the wireless communication network. Further, the MN receives Registration Reply (Binding Acknowledge in NEMO), which is handover completion information returned from the HA, and disconnects from the handover source wireless communication network. Communication is performed via a wireless communication network.
　すなわち、ＭＢＢ方式によるハンドオーバでは、ＨＡにハンドオーバ先のＣｏＡが登録された後も、ＭＮが、ＨＡからのハンドオーバ完了情報を受信して、ハンドオーバ先の無線通信ネットワークからパケットの送信を開始するまでは、ＭＮは、ハンドオーバ元の無線通信ネットワークからパケットを送信することになる。 That is, in the handover by the MBB method, after the handover destination CoA is registered in the HA, until the MN receives the handover completion information from the HA and starts transmitting a packet from the handover destination wireless communication network. The MN transmits a packet from the handover source wireless communication network.
　このため、ＨＡに１つのＣｏＡのみを登録して、ＭＮからＨＡを経てＣＮへパケットを送信する場合は、ＨＡにハンドオーバ先のＣｏＡが登録された後に、ハンドオーバ元の無線通信ネットワークを経てＨＡに到達したパケットは、ＣＮに転送されずに破棄されて、ロストすることになる。このパケットのロスト量は、ハンドオーバ元の無線通信ネットワークにおけるＭＮからＨＡまでの上りの絶対遅延時間が長いほど多くなり、また、ハンドオーバ先の無線通信ネットワークにおけるＨＡからＭＮまでの下りの絶対遅延時間が長いほど多くなる。 For this reason, when only one CoA is registered in the HA and a packet is transmitted from the MN to the CN via the HA, after the handover destination CoA is registered in the HA, the HA is transmitted to the HA via the handover source wireless communication network. The arrived packet is discarded without being transferred to the CN and lost. The lost amount of this packet increases as the absolute delay time from the MN to the HA in the handover source wireless communication network increases, and the downlink absolute delay time from the HA to the MN in the handover destination wireless communication network. The longer you go, the more.
　その結果、ＶｏＩＰなどのリアルタイムアプリケーションでの通信中に、ハンドオーバした場合は、ＣＮ側において、パケットロスにより音が切れて、無音が発生し、再生品質およびリアルタイム性の低下を招くことになる。 As a result, when a handover is performed during communication using a real-time application such as VoIP, sound is cut off due to packet loss on the CN side, and silence is generated, leading to deterioration in reproduction quality and real-time property.
　また、ＨＡに１つのＣｏＡのみを登録して、ＣＮからの送信パケットをＭＮへ転送する場合において、ハンドオーバ元の下りの絶対遅延時間が、ハンドオーバ先の下りの絶対遅延時間よりも長いと、ＭＮは、ハンドオーバ先からのハンドオーバ完了情報に基づいて無線通信ネットワークを切替えるので、切替え後、ハンドオーバ元の無線通信ネットワークを介してＨＡから送信されていたパケットがハンドオーバ元の無線通信ネットワークを切断した後では受信できなくなって、パケットのロストが生じることになる。このパケットのロスト量は、ハンドオーバ元の無線通信ネットワークにおけるＨＡからＭＮからまでの下りの絶対遅延時間が、ハンドオーバ先の無線通信ネットワークにおけるそれよりも長いほど、多くなる。 In addition, when only one CoA is registered in the HA and a transmission packet from the CN is transferred to the MN, if the absolute delay time of the handover source downlink is longer than the absolute delay time of the handover destination downlink, Since the wireless communication network is switched based on the handover completion information from the handover destination, after the switching, the packet transmitted from the HA via the handover source wireless communication network is disconnected from the handover source wireless communication network. The packet cannot be received and the packet is lost. The lost amount of this packet increases as the absolute delay time of the downlink from the HA to the MN in the handover source wireless communication network is longer than that in the handover destination wireless communication network.
　その結果、ＶｏＩＰなどのリアルタイムアプリケーションでの通信中に、ハンドオーバした場合は、ＭＮ側においても、同様に、パケットロスにより音が切れて、無音が発生し、再生品質およびリアルタイム性の低下を招くことになる。 As a result, when a handover is performed during communication using a real-time application such as VoIP, the sound is cut off due to packet loss on the MN side as well, and silence is generated, leading to deterioration in reproduction quality and real-time performance. become.
　このようなパケットロスによる無音の発生を防止する方法として、例えば、パケットロスの前後の音を繋げるように再生処理することが考えられる。しかし、この場合は、文章が連続しなくなるなど、音声を聞くユーザに違和感を与えることになる。 As a method for preventing the occurrence of silence due to such packet loss, for example, it is conceivable to perform reproduction processing so as to connect sounds before and after the packet loss. However, in this case, the user who listens to the voice feels uncomfortable, for example, the sentences are not continuous.
　したがって、かかる点に鑑みてなされた本発明の第１の目的は、パケットロスを生じることなく、異なる無線通信ネットワークへハンドオーバでき、常に安定した再生品質およびリアルタイム性を維持できる無線通信装置を提供することにある。 Accordingly, a first object of the present invention made in view of such a point is to provide a wireless communication apparatus that can be handed over to a different wireless communication network without causing packet loss and can always maintain stable reproduction quality and real-time performance. There is.
　さらに、本発明の第２の目的は、異なる無線通信ネットワークへハンドオーバする無線通信装置に対して、パケットロスを生じることなくパケットを送信でき、常に安定した再生品質およびリアルタイム性を維持できる通信装置を提供することにある。 Furthermore, a second object of the present invention is to provide a communication device that can transmit a packet without causing packet loss to a wireless communication device handed over to a different wireless communication network, and can always maintain stable reproduction quality and real-time performance. It is to provide.
　上記第１の目的を達成する第１の観点に係る無線通信装置の発明は、
　第１無線通信ネットワーク、および該第１無線通信ネットワークと異なる第２無線通信ネットワークに接続して無線通信を実行する無線通信部と、
　該無線通信部を介してリアルタイム通信系のアプリケーションを実行する実行部と、
　前記第１無線通信ネットワークに接続して前記アプリケーションを実行中に、当該第１無線通信ネットワークにおける無線リンクの通信品質を取得する通信品質取得部と、
　該通信品質取得部により取得した前記通信品質に基づいて、前記第１無線通信ネットワークから前記第２無線通信ネットワークへのハンドオーバの準備を開始するか否かを決定する決定部と、
　前記決定部によりハンドオーバ準備の開始を決定すると、前記第１無線通信ネットワークを介してデータを送信するとともに、該データを所定時間蓄積し、ハンドオーバ後に、該蓄積したデータを前記第２無線通信ネットワークを介して送信するよう制御する制御部と、
　を備えることを特徴とするものである。 The invention of the wireless communication apparatus according to the first aspect for achieving the first object is as follows:
A wireless communication unit that performs wireless communication by connecting to a first wireless communication network and a second wireless communication network different from the first wireless communication network;
An execution unit that executes an application of a real-time communication system via the wireless communication unit;
A communication quality acquisition unit for acquiring communication quality of a radio link in the first wireless communication network while executing the application by connecting to the first wireless communication network;
A determination unit that determines whether to start preparation for handover from the first wireless communication network to the second wireless communication network based on the communication quality acquired by the communication quality acquisition unit;
When the determination unit determines the start of handover preparation, the data is transmitted through the first wireless communication network, the data is stored for a predetermined time, and after the handover, the stored data is transferred to the second wireless communication network. A control unit controlling to transmit via,
It is characterized by providing.
　第２の観点に係る発明は、第１の観点に係る無線通信装置において、
　前記アプリケーションの実行中に、前記決定部がハンドオーバ準備の開始を決定すると、前記通信品質取得部が取得した通信品質に基づいてハンドオーバを開始するまでのハンドオーバ準備時間を推定する推定部と、
　前記決定部がハンドオーバ準備の開始を決定すると、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間を計測する計測部と、を備え、
　前記制御部は、前記計測部により計測した前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間と、前記推定部により推定した前記ハンドオーバ準備時間とに基づいて、前記データを蓄積する開始時間を決定することを特徴とするものである。 The invention according to a second aspect is the wireless communication device according to the first aspect,
When the determination unit determines the start of handover preparation during the execution of the application, an estimation unit that estimates a handover preparation time until the handover is started based on the communication quality acquired by the communication quality acquisition unit;
When the determination unit determines the start of handover preparation, a measurement unit that measures respective delay times in the first wireless communication network and the second wireless communication network, and
The control unit accumulates the data based on respective delay times in the first wireless communication network and the second wireless communication network measured by the measurement unit and the handover preparation time estimated by the estimation unit. It is characterized by determining a start time to be performed.
　第３の観点に係る発明は、第１の観点に係る無線通信装置において、
　前記決定部がハンドオーバ準備の開始を決定すると、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間を計測する計測部と、を備え、
　前記制御部は、前記計測部により計測した前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間に基づいて、前記データを蓄積する所定時間を決定することを特徴とするものである。 The invention according to a third aspect is the wireless communication device according to the first aspect,
When the determination unit determines the start of handover preparation, a measurement unit that measures respective delay times in the first wireless communication network and the second wireless communication network, and
The control unit determines a predetermined time for storing the data based on respective delay times in the first wireless communication network and the second wireless communication network measured by the measurement unit. is there.
　第４の観点に係る発明は、第１，２または３の観点に係る無線通信装置において、
　送信データを符号化する符号化部を備え、
　該符号化部は、前記決定部がハンドオーバ準備の開始を決定する前の符号化ビットレートよりも低いレートで、前記蓄積するデータを符号化することを特徴とするものである。 The invention according to a fourth aspect is the wireless communication device according to the first, second or third aspect,
An encoding unit for encoding transmission data;
The encoding unit encodes the accumulated data at a rate lower than an encoding bit rate before the determination unit determines start of handover preparation.
　上記第２の目的を達成する第５の観点に係る通信装置の発明は、
　通信ネットワークに接続して通信を実行する通信部と、
　該通信部を介してリアルタイム通信系のアプリケーションを実行する実行部と、
　前記アプリケーションの通信相手である無線通信装置が、通信中の第１無線通信ネットワークから該第１無線通信ネットワークと異なる第２無線通信ネットワークヘハンドオーバするハンドオーバの情報を前記無線通信装置から受信すると、前記通信ネットワークを介してデータを送信するとともに、該データを所定時間蓄積し、前記無線通信装置のハンドオーバ後に、該蓄積したデータを前記無線通信装置へ送信するよう制御する制御部と、
　を備えることを特徴とするものである。 The invention of the communication device according to the fifth aspect of achieving the second object is as follows:
A communication unit that connects to a communication network and executes communication;
An execution unit that executes an application of a real-time communication system via the communication unit;
When a wireless communication device that is a communication partner of the application receives handover information from the wireless communication device that performs handover from the first wireless communication network in communication to a second wireless communication network different from the first wireless communication network, A control unit for transmitting data via a communication network, storing the data for a predetermined time, and controlling the stored data to be transmitted to the wireless communication device after handover of the wireless communication device;
It is characterized by providing.
　第６の観点に係る発明は、第５の観点に係る通信装置において、
　前記制御部は、前記ハンドオーバの情報に含まれる、ハンドオーバの準備時間と、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間と、前記通信ネットワークにおける遅延時間とに基づいて、前記データを蓄積する開始時間を決定することを特徴とするものである。 The invention according to a sixth aspect is the communication apparatus according to the fifth aspect,
The control unit, based on the handover preparation time, the delay time in the first radio communication network and the second radio communication network, and the delay time in the communication network, included in the handover information, A start time for storing the data is determined.
　第７の観点に係る発明は、第５の観点に係る通信装置において、
　前記制御部は、前記ハンドオーバの情報に含まれる、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間に基づいて、前記データを蓄積する所定時間を決定することを特徴とするものである。 The invention according to a seventh aspect is the communication apparatus according to the fifth aspect,
The control unit determines a predetermined time for storing the data based on respective delay times in the first wireless communication network and the second wireless communication network included in the handover information. Is.
　第８の観点に係る発明は、第６の観点に係る通信装置において、
　前記制御部は、前記ハンドオーバの情報に含まれる、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間に基づいて、前記データを蓄積する所定時間を決定することを特徴とするものである。 The invention according to an eighth aspect is the communication apparatus according to the sixth aspect,
The control unit determines a predetermined time for storing the data based on respective delay times in the first wireless communication network and the second wireless communication network included in the handover information. Is.
　第９の観点に係る発明は、第５，６，７または８の観点に係る通信装置において、
　送信データを符号化する符号化部を備え、
　前記符号化部は、前記ハンドオーバの情報を受信する前の符号化ビットレートよりも低いレートで、前記蓄積するデータを符号化することを特徴とするものである。 The invention according to a ninth aspect is the communication device according to the fifth, sixth, seventh or eighth aspect,
An encoding unit for encoding transmission data;
The encoding unit encodes the accumulated data at a rate lower than an encoding bit rate before receiving the handover information.
　本発明の無線通信装置は、第１無線通信ネットワークから第２無線通信ネットワークへのハンドオーバの準備の開始を決定すると、第１無線通信ネットワークを介してデータを送信するとともに、該データを所定時間蓄積して、その蓄積したデータをハンドオーバ後に、第２無線通信ネットワークを介して送信する。したがって、ハンドオーバによってロストすると思われる所定時間のデータを送信しながら蓄積し、その蓄積したデータをハンドオーバ後に送信することができる。これにより、パケットロスを生じることなく、異なる無線通信ネットワークへハンドオーバでき、常に安定した再生品質およびリアルタイム性を維持することができる。 When the wireless communication device of the present invention determines to start preparation for handover from the first wireless communication network to the second wireless communication network, the wireless communication device transmits data via the first wireless communication network and stores the data for a predetermined time. Then, the stored data is transmitted via the second wireless communication network after the handover. Therefore, it is possible to accumulate while transmitting data for a predetermined time that is thought to be lost due to handover, and transmit the accumulated data after the handover. As a result, handover to a different wireless communication network can be performed without causing packet loss, and stable reproduction quality and real-time performance can always be maintained.
　また、本発明の通信装置は、通信相手である無線通信装置から、該無線通信装置が通信中の第１無線通信ネットワークから他の第２無線通信ネットワークヘハンドオーバするハンドオーバの情報を受信すると、無線通信装置にデータを送信しながら、該データを所定時間蓄積し、その蓄積したデータを無線通信装置のハンドオーバ後に送信する。したがって、無線通信装置からのハンドオーバの情報に基づいて、当該無線通信装置が異なる無線通信ネットワークへハンドオーバする際にロストすると思われる所定時間のデータを送信しながら蓄積して、その蓄積したデータをハンドオーバ後に送信することができる。これにより、パケットロスを生じることなく、常に安定した再生品質およびリアルタイム性を維持することができる。 In addition, when the communication apparatus of the present invention receives information on handover from the first wireless communication network with which the wireless communication apparatus is communicating to another second wireless communication network from the wireless communication apparatus that is the communication partner, While transmitting data to the communication device, the data is stored for a predetermined time, and the stored data is transmitted after the handover of the wireless communication device. Therefore, based on the handover information from the wireless communication device, the wireless communication device accumulates while transmitting data for a predetermined time that is considered to be lost when the wireless communication device hands over to a different wireless communication network, and the stored data is handed over. Can be sent later. As a result, stable reproduction quality and real-time performance can always be maintained without causing packet loss.
本発明の第１実施の形態に係る無線通信装置が使用可能な通信ネットワークの概略構成を示す図である。It is a figure which shows schematic structure of the communication network which can use the radio | wireless communication apparatus which concerns on 1st Embodiment of this invention. 図１に示した無線通信装置の概略構成を示すブロック図である。It is a block diagram which shows schematic structure of the radio | wireless communication apparatus shown in FIG. 図２に示した無線通信装置の電話機能部の概略構成を示す機能ブロック図である。It is a functional block diagram which shows schematic structure of the telephone function part of the radio | wireless communication apparatus shown in FIG. 図２に示したハンドオーバ制御部によるハンドオーバ準備時間の算出方法を説明するための図である。FIG. 3 is a diagram for explaining a method for calculating a handover preparation time by the handover control unit shown in FIG. 2. 絶対遅延時間取得方法の一例を説明するための図である。It is a figure for demonstrating an example of the absolute delay time acquisition method. 図２に示したハンドオーバ制御部に記憶する無線状態とスループットとの変換テーブルの一例を示す図である。FIG. 3 is a diagram illustrating an example of a conversion table between radio conditions and throughput stored in a handover control unit illustrated in FIG. 2. 図１に示した無線通信装置とＨＡとの間のハンドオーバ処理を説明するためのシーケンス図である。FIG. 2 is a sequence diagram for explaining a handover process between the wireless communication apparatus shown in FIG. 1 and an HA. 図７に示したハンドオーバ処理によるパケットロスの発生を説明するための図である。It is a figure for demonstrating generation | occurrence | production of the packet loss by the hand-over process shown in FIG. 図２に示した電話機能部によるハンドオーバ時のデータ送信処理の概要を説明するための図である。It is a figure for demonstrating the outline | summary of the data transmission process at the time of the handover by the telephone function part shown in FIG. 図３に示した送信制御部によるハンドオーバ時の動作を示すフローチャートである。FIG. 4 is a flowchart showing an operation at the time of handover by a transmission control unit shown in FIG. 3. FIG. 図１に示した無線通信装置がハンドオーバ時に送信制御を行った場合の通信装置との間における送受信パケットの状態を示す図である。It is a figure which shows the state of the transmission / reception packet between communication apparatuses when the radio | wireless communication apparatus shown in FIG. 1 performs transmission control at the time of a handover. ハンドオーバ時に送信制御を行わなかった場合の無線通信装置と通信装置との間における送受信パケットの状態を示す図である。It is a figure which shows the state of the transmission / reception packet between a radio | wireless communication apparatus and a communication apparatus at the time of not performing transmission control at the time of a hand-over. 図１に示した通信装置の概略構成を示す機能ブロック図である。It is a functional block diagram which shows schematic structure of the communication apparatus shown in FIG. 図１３に示した電話機能部の概略構成を示す機能ブロック図である。It is a functional block diagram which shows schematic structure of the telephone function part shown in FIG. 図１４に示した電話機能部の要部の動作を示すシーケンス図である。It is a sequence diagram which shows operation | movement of the principal part of the telephone function part shown in FIG. 図１に示した無線通信装置、ＨＡおよび通信装置間でのハンドオーバ情報の流れを示すシーケンス図である。FIG. 2 is a sequence diagram illustrating a flow of handover information between the wireless communication device, the HA, and the communication device illustrated in FIG. 1. 図１４に示した再生速度計算部の動作を示すフローチャートである。15 is a flowchart showing an operation of a reproduction speed calculation unit shown in FIG. 図１に示した通信装置によるパケットの再生制御を説明するための図である。It is a figure for demonstrating the reproduction | regeneration control of the packet by the communication apparatus shown in FIG. 図１４に示したジッタバッファ制御部による受信パケットの再生速度制御方法の一例を説明するための図である。FIG. 15 is a diagram for describing an example of a reception packet reproduction rate control method by the jitter buffer control unit illustrated in FIG. 14. 本発明の第２実施の形態に係る通信装置が使用可能な通信ネットワークの概略構成を示す図である。It is a figure which shows schematic structure of the communication network which can use the communication apparatus which concerns on 2nd Embodiment of this invention. 図２０に示した無線通信装置の概略構成を示すブロック図である。It is a block diagram which shows schematic structure of the radio | wireless communication apparatus shown in FIG. 図２０に示した無線通信装置とＨＡとの間のハンドオーバ処理を説明するためのシーケンス図である。FIG. 21 is a sequence diagram for explaining a handover process between the wireless communication apparatus shown in FIG. 20 and the HA. 図２２に示したハンドオーバ処理によるパケットロスの発生を説明するための図である。It is a figure for demonstrating generation | occurrence | production of the packet loss by the hand-over process shown in FIG. 図２０に示した通信装置の概略構成を示す機能ブロック図である。It is a functional block diagram which shows schematic structure of the communication apparatus shown in FIG. 図２４に示した電話機能部の概略構成を示す機能ブロック図である。It is a functional block diagram which shows schematic structure of the telephone function part shown in FIG. 図２５に示した電話機能部によるハンドオーバ時のデータ送信処理の概要を説明するための図である。It is a figure for demonstrating the outline | summary of the data transmission process at the time of the handover by the telephone function part shown in FIG. 図２５に示した送信制御部によるハンドオーバ時の動作を示すフローチャートである。It is a flowchart which shows the operation | movement at the time of the handover by the transmission control part shown in FIG. ハンドオーバ時に図２０に示した通信装置が送信制御を行った場合の無線通信装置における受信パケットの状態を示す図である。It is a figure which shows the state of the received packet in a radio | wireless communication apparatus when the communication apparatus shown in FIG. 20 performs transmission control at the time of a hand-over. ハンドオーバ時に通信装置が送信制御を行わなかった場合の無線通信装置における受信パケットの状態を示す図である。It is a figure which shows the state of the received packet in a radio | wireless communication apparatus when a communication apparatus does not perform transmission control at the time of a handover. 図２１に示した無線通信装置の電話機能部の概略構成を示す機能ブロック図である。It is a functional block diagram which shows schematic structure of the telephone function part of the radio | wireless communication apparatus shown in FIG. 図３０に示した電話機能部の要部の動作を示すシーケンス図である。FIG. 31 is a sequence diagram showing an operation of a main part of the telephone function unit shown in FIG. 30. 図２０に示した無線通信装置によるパケットの再生制御を説明するための図である。It is a figure for demonstrating the reproduction | regeneration control of the packet by the radio | wireless communication apparatus shown in FIG.
符号の説明Explanation of symbols
　１１　無線通信装置
　１２　通信装置
　１２ａ　送受話器
　１５　第１無線通信ネットワーク
　１５ａ　基地局
　１６　第２無線通信ネットワーク
　１６ａ　アクセスポイント
　１８　インターネット
　２１，２２，２４　ＳＩＰサーバ
　２３　ホームエージェント（ＨＡ）
　３１　第１無線Ｉ／Ｆ
　３２　第２無線Ｉ／Ｆ
　３３　電話機能部
　３４　通信処理部
　３５　無線情報取得部
　３６　ハンドオーバ制御部
　４４　エンコーダ
　４７　ジッタバッファ
　５０　ジッタバッファ監視部
　５１　ジッタバッファ制御部
　５５　ハンドオーバ情報取得部
　５６　送信制御部
　５７　送信バッファ
　６１　計測用サーバ
　６２　第１インフォメーションサーバ
　６３　第２インフォメーションサーバ
　１２１　無線通信装置
　１２２　通信装置
　１２２ａ　送受話器
　１４４　エンコーダ
　１４７　ジッタバッファ
　１５０　ジッタバッファ監視部
　１５１　ジッタバッファ制御部
　１５５　ハンドオーバ情報取得部
　１５６　送信制御部
　１５７　送信バッファ
　１８１　ネットワークＩ／Ｆ
　１８２　通信処理部
　１８３　電話機能部 DESCRIPTION OF SYMBOLS 11 Wireless communication apparatus 12 Communication apparatus 12a Handset 15 1st wireless communication network 15a Base station 16 2nd wireless communication network 16a Access point 18 Internet 21, 22, 24 SIP server 23 Home agent (HA)
31 First wireless I / F
32 Second wireless I / F
33 Telephone function unit 34 Communication processing unit 35 Wireless information acquisition unit 36 Handover control unit 44 Encoder 47 Jitter buffer 50 Jitter buffer monitoring unit 51 Jitter buffer control unit 55 Handover information acquisition unit 56 Transmission control unit 57 Transmission buffer 61 Measurement server 62 1 Information Server 63 2nd Information Server 121 Wireless Communication Device 122 Communication Device 122a Handset 144 Encoder 147 Jitter Buffer 150 Jitter Buffer Monitoring Unit 151 Jitter Buffer Control Unit 155 Handover Information Acquisition Unit 156 Transmission Control Unit 157 Transmission Buffer 181 Network I / F
182 Communication processing unit 183 Telephone function unit
　以下、本発明の実施の形態について、図を参照して説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
（第１実施の形態）
　図１は、本発明の第１実施の形態に係る無線通信装置が使用可能な通信ネットワークの概略構成を示す図である。図１において、移動ノードである無線通信装置（ＭＮ）１１は、対向ノードである通信装置（ＣＮ）１２との間で、リアルタイム通信系のアプリケーションであるＶｏＩＰによる通話を行うものとする。無線通信装置１１は、第１無線通信ネットワーク１５と第２無線通信ネットワーク１６との間で、ハンドオーバが可能となっている。第１無線通信ネットワーク１５および第２無線通信ネットワーク１６は、インターネット１８に結合されている。 (First embodiment)
FIG. 1 is a diagram showing a schematic configuration of a communication network that can be used by the wireless communication apparatus according to the first embodiment of the present invention. In FIG. 1, it is assumed that a wireless communication device (MN) 11 that is a mobile node makes a call with a communication device (CN) 12 that is an opposite node by VoIP that is a real-time communication system application. The wireless communication device 11 can be handed over between the first wireless communication network 15 and the second wireless communication network 16. The first wireless communication network 15 and the second wireless communication network 16 are coupled to the Internet 18.
　ここで、第１無線通信ネットワーク１５は、例えばｃｄｍａ２０００　１ｘＥＶ－ＤＯ（Code Division Multiple Access 2000 1x Evolution Data Only）の携帯電話ネットワークを想定し、第２無線通信ネットワーク１６は、例えば無線ＬＡＮ（Local Area Network）を想定する。第２無線通信ネットワーク１６における上りの絶対遅延時間は、第１無線通信ネットワーク１５における上りの絶対遅延時間よりも短いと仮定する。なお、図１において、符号１５ａは、第１無線通信ネットワーク１５の基地局を示し、符号１６ａは、第２無線通信ネットワーク１６のアクセスポイントを示す。 Here, the first wireless communication network 15 is assumed to be, for example, a mobile phone network of cdma2000 1xEV-DO (Code Division Multiple Access 2000-1x Evolution Data Only), and the second wireless communication network 16 is, for example, a wireless LAN (Local Area Network). ) Is assumed. It is assumed that the uplink absolute delay time in the second radio communication network 16 is shorter than the uplink absolute delay time in the first radio communication network 15. In FIG. 1, reference numeral 15 a indicates a base station of the first wireless communication network 15, and reference numeral 16 a indicates an access point of the second wireless communication network 16.
　通信装置１２は、例えば送受話器１２ａが接続され、電話機能部としてのソフトフォンがインストールされたパーソナルコンピュータからなり、図示しないインターネットサービスプロバイダを介してインターネット１８に接続されている。 The communication device 12 includes, for example, a personal computer to which a handset 12a is connected and a softphone as a telephone function unit is installed, and is connected to the Internet 18 through an Internet service provider (not shown).
　また、第１無線通信ネットワーク１５および第２無線通信ネットワーク１６には、それぞれ通信を制御するＳＩＰ（Session Initiation Protocol）サーバ２１および２２が接続されている。さらに、インターネット１８には、無線通信装置１１宛の受信パケットを、無線通信装置１１が接続されている無線通信ネットワークに転送するホームエージェント（ＨＡ）２３と、通信を制御するＳＩＰサーバ２４とが接続されている。 Further, SIP (Session Initiation Protocol) servers 21 and 22 for controlling communication are connected to the first wireless communication network 15 and the second wireless communication network 16, respectively. Further, a home agent (HA) 23 that transfers a received packet addressed to the wireless communication device 11 to the wireless communication network to which the wireless communication device 11 is connected and a SIP server 24 that controls communication are connected to the Internet 18. Has been.
　図１に示す通信ネットワークにおいては、ＨＡ２３に、無線通信装置１１が本来属する無線通信ネットワークで用いるホームアドレスを登録するとともに、ハンドオーバ時に、ハンドオーバ先の無線通信ネットワークのＩＰアドレスを気付けアドレス（ＣｏＡ：care of address）として登録することにより、異なる無線通信ネットワーク間でのハンドオーバが可能となる。なお、このようなＩＰモビリティ技術については、上述したモバイルＩＰや、ＮＥＭＯにおいて公知であるので、ここでは詳細な説明は省略する。 In the communication network shown in FIG. 1, the home address used in the wireless communication network to which the wireless communication apparatus 11 originally belongs is registered in the HA 23, and the IP address of the handover destination wireless communication network is taken care of (CoA: care) at the time of handover. By registering as “of address”, handover between different wireless communication networks becomes possible. Note that such IP mobility technology is well known in the above-described mobile IP and NEMO, and thus detailed description thereof is omitted here.
　図１において、無線通信装置１１は、ＨＡ２３に第１無線通信ネットワーク１５のＩＰアドレスを気付けアドレス（第１無線ＣｏＡ）として登録して、第１無線通信ネットワーク１５を介して通信装置１２と通信を行っている状態から、第２無線通信ネットワーク１６へハンドオーバするものとする。 In FIG. 1, the wireless communication device 11 registers the IP address of the first wireless communication network 15 in the HA 23 as a care-of address (first wireless CoA), and communicates with the communication device 12 via the first wireless communication network 15. It is assumed that handover is performed from the current state to the second wireless communication network 16.
　図２は、図１に示した本実施の形態に係る無線通信装置１１の概略構成を示す機能ブロック図である。無線通信装置１１は、第１無線通信ネットワーク１５に対応する第１無線Ｉ／Ｆ（インターフェース）３１と、第２無線通信ネットワーク１６に対応する第２無線Ｉ／Ｆ３２と、ＶｏＩＰのアプリケーションを実行する電話機能部３３と、第１無線通信ネットワーク１５および第２無線通信ネットワーク１６への接続を制御する通信処理部３４と、第１無線通信ネットワーク１５および第２無線通信ネットワーク１６の無線情報を取得する無線情報取得部３５と、第１無線通信ネットワーク１５と第２無線通信ネットワーク１６との間のハンドオーバを制御するハンドオーバ制御部３６と、を有する。 FIG. 2 is a functional block diagram showing a schematic configuration of the wireless communication apparatus 11 according to the present embodiment shown in FIG. The wireless communication device 11 executes a first wireless I / F (interface) 31 corresponding to the first wireless communication network 15, a second wireless I / F 32 corresponding to the second wireless communication network 16, and a VoIP application. The wireless information of the telephone function unit 33, the communication processing unit 34 that controls connection to the first wireless communication network 15 and the second wireless communication network 16, and the wireless information of the first wireless communication network 15 and the second wireless communication network 16 is acquired. A wireless information acquisition unit 35; and a handover control unit 36 that controls a handover between the first wireless communication network 15 and the second wireless communication network 16.
　通信処理部３４は、無線通信を実行する無線通信部を構成するもので、電話機能部３３と通信装置１２との間で、第１無線通信ネットワーク１５または第２無線通信ネットワーク１６を介して通話を行うとともに、ハンドオーバ制御部３６による制御のもとに、ＨＡ２３と通信するように、第１無線Ｉ／Ｆ３１または第２無線Ｉ／Ｆ３２の接続を制御する。 The communication processing unit 34 constitutes a wireless communication unit that performs wireless communication, and calls between the telephone function unit 33 and the communication device 12 via the first wireless communication network 15 or the second wireless communication network 16. And the connection of the first wireless I / F 31 or the second wireless I / F 32 is controlled to communicate with the HA 23 under the control of the handover control unit 36.
　無線情報取得部３５は、無線情報として、第１無線Ｉ／Ｆ３１および第２無線Ｉ／Ｆ３２から、それぞれ対応する第１無線通信ネットワーク１５および第２無線通信ネットワーク１６の通信品質を取得し、その取得した通信品質をハンドオーバ制御部３６に供給する。ここで、通信品質は、例えば、無線状態を表すＲＳＳＩ（Received Signal Strength Indicator）を取得する。したがって、無線情報取得部３５は、無線リンクの通信品質を取得する通信品質取得部を構成する。 The wireless information acquisition unit 35 acquires the communication quality of the corresponding first wireless communication network 15 and second wireless communication network 16 from the first wireless I / F 31 and the second wireless I / F 32 as wireless information, The acquired communication quality is supplied to the handover control unit 36. Here, as the communication quality, for example, RSSI (Received Signal Signal Strength Indicator) indicating a wireless state is acquired. Therefore, the radio information acquisition unit 35 constitutes a communication quality acquisition unit that acquires the communication quality of the radio link.
　ハンドオーバ制御部３６は、無線情報取得部３５からの通信品質に基づいて、ハンドオーバを予定するか否か、すなわちハンドオーバの準備を開始するか否かの決定を含むハンドオーバ情報を生成し、そのハンドオーバ情報に基づいてハンドオーバを制御する。 Based on the communication quality from the radio information acquisition unit 35, the handover control unit 36 generates handover information including a decision whether to schedule a handover, that is, whether to start preparation for handover, and the handover information Based on the above, handover is controlled.
　図３は、図２に示した無線通信装置１１の電話機能部３３の概略構成を示す機能ブロック図である。電話機能部３３は、例えばソフトフォンからなり、公知のソフトフォンの構成と同様に、ボタン入力部４１、画面表示部４２、マイク４３、エンコーダ４４、パケット送信部４５、パケット受信部４６、ジッタバッファ４７、デコーダ４８、スピーカ４９、ジッタバッファ監視部５０、ジッタバッファ制御部５１、ＳＩＰ制御部５２、および全体の動作を制御する全体制御部５３を有する。 FIG. 3 is a functional block diagram showing a schematic configuration of the telephone function unit 33 of the wireless communication apparatus 11 shown in FIG. The telephone function unit 33 is composed of, for example, a soft phone, and has a button input unit 41, a screen display unit 42, a microphone 43, an encoder 44, a packet transmission unit 45, a packet reception unit 46, a jitter buffer, as in the configuration of a known soft phone. 47, a decoder 48, a speaker 49, a jitter buffer monitoring unit 50, a jitter buffer control unit 51, a SIP control unit 52, and an overall control unit 53 for controlling the overall operation.
　全体制御部５３は、ボタン入力部４１や画面表示部４２を介して、ユーザの操作情報を取得し、その取得情報に基づいて全体の動作を制御する。また、ＳＩＰ制御部５２は、通話の開始や終了のＳＩＰの手続きを制御する。通話中において、マイク４３から取得された音声データは、符号化部であるエンコーダ４４でエンコードされ、そのエンコードされたデータは、パケット送信部４５からパケットに入れられて、通信処理部３４を経て通信装置１２へ送信される。 The overall control unit 53 acquires user operation information via the button input unit 41 and the screen display unit 42, and controls the overall operation based on the acquired information. The SIP control unit 52 controls SIP procedures for starting and ending a call. During a call, the audio data acquired from the microphone 43 is encoded by the encoder 44 which is an encoding unit, and the encoded data is put into a packet from the packet transmission unit 45 and communicated via the communication processing unit 34. Transmitted to the device 12.
　また、通信処理部３４を経てパケット受信部４６で受信された通信装置１２からのパケットは、ジッタバッファ４７に一旦取り込まれてから読み出され、その読み出されたパケットは、デコーダ４８でペイロード部分がデコードされて、スピーカ４９から再生音声として出力される。なお、ジッタバッファ４７のパケットの受信状況や、ジッタバッファ４７内のパケット数（データ量）の状態は、ジッタバッファ監視部５０で監視され、その監視結果に基づいて、ジッタバッファ制御部５１により、ジッタバッファ４７からのパケットの読み出し速度や、受信したパケットの破棄などの処理が制御される。 The packet from the communication device 12 received by the packet receiving unit 46 via the communication processing unit 34 is once fetched into the jitter buffer 47 and then read out. Are decoded and output as reproduced sound from the speaker 49. The reception status of packets in the jitter buffer 47 and the number of packets (data amount) in the jitter buffer 47 are monitored by the jitter buffer monitoring unit 50. Based on the monitoring result, the jitter buffer control unit 51 Processing such as a packet reading speed from the jitter buffer 47 and discarding of the received packet is controlled.
　本実施の形態に係る無線通信装置１１は、電話機能部３３に、さらに、ハンドオーバ情報取得部５５、送信制御部５６および送信バッファ５７を備える。ハンドオーバ情報取得部５５は、ハンドオーバ制御部３６からのハンドオーバ情報を一定間隔毎に監視して、ハンドオーバの予定を決定するハンドオーバ予定決定情報を取得する。ハンドオーバ予定決定情報を取得した場合は、ハンドオーバ情報取得部５５は、さらに、ハンドオーバ制御部３６から所要のハンドオーバ情報を取得して、その取得した所要のハンドオーバ情報を送信制御部５６に供給する。 The radio communication apparatus 11 according to the present embodiment further includes a telephone function unit 33, a handover information acquisition unit 55, a transmission control unit 56, and a transmission buffer 57. The handover information acquisition unit 55 monitors handover information from the handover control unit 36 at regular intervals, and acquires handover schedule determination information for determining a handover schedule. When the handover schedule determination information is acquired, the handover information acquisition unit 55 further acquires the required handover information from the handover control unit 36 and supplies the acquired required handover information to the transmission control unit 56.
　送信制御部５６は、エンコーダ４４による送信データの符号化ビットレートおよびエンコーダ４４からパケット送信部４５へのデータの送信を制御する。すなわち、送信制御部５６は、ハンドオーバ情報取得部５５からハンドオーバ情報が供給されない通常の通話状態では、エンコーダ４４でエンコードされたデータをパケット送信部４５に直接送信する。これに対し、ハンドオーバ情報取得部５５からハンドオーバ情報が供給された場合は、送信制御部５６は、そのハンドオーバ情報に基づいて、ハンドオーバによってロストすると思われるエンコーダ４４からのデータを送信バッファ５７に蓄積し、その蓄積したデータをハンドオーバ完了後にパケット送信部４５に送信するように制御する。この送信制御部５６による送信制御については、さらに後述する。 The transmission control unit 56 controls the encoding bit rate of transmission data by the encoder 44 and the transmission of data from the encoder 44 to the packet transmission unit 45. That is, the transmission control unit 56 directly transmits the data encoded by the encoder 44 to the packet transmission unit 45 in a normal call state in which handover information is not supplied from the handover information acquisition unit 55. On the other hand, when the handover information is supplied from the handover information acquisition unit 55, the transmission control unit 56 stores the data from the encoder 44 that seems to be lost due to the handover in the transmission buffer 57 based on the handover information. The accumulated data is controlled to be transmitted to the packet transmitter 45 after the handover is completed. The transmission control by the transmission control unit 56 will be further described later.
　したがって、本実施の形態に係る無線通信装置１１において、電話機能部３３は、リアルタイム通信系のアプリケーションを実行する実行部、および当該アプリケーションのデータの送信を制御する制御部を構成する。 Therefore, in the wireless communication device 11 according to the present embodiment, the telephone function unit 33 configures an execution unit that executes a real-time communication system application and a control unit that controls transmission of data of the application.
　以下、本実施の形態に係る無線通信装置１１の動作について説明する。 Hereinafter, the operation of the wireless communication apparatus 11 according to the present embodiment will be described.
　先ず、主としてハンドオーバ制御部３６の動作について説明する。ハンドオーバ制御部３６は、第１無線Ｉ／Ｆ３１および第２無線Ｉ／Ｆ３２から無線情報取得部３５を経由してそれぞれ取得した通信品質に基づいて、ハンドオーバの予定を決定する。例えば、第１無線通信ネットワーク１５と無線リンクを形成して通話を行っている場合に、第１無線Ｉ／Ｆ３１から取得した通信品質がハンドオーバ予定決定閾値よりも悪くなり、かつ第２無線Ｉ／Ｆ３２の通信品質がハンドオーバ予定決定閾値以上となった場合には、ハンドオーバ制御部３６は、第２無線通信ネットワーク１６へのハンドオーバ予定を決定する、すなわちハンドオーバ準備の開始を決定する。なお、通話に使用していない第２無線通信ネットワーク１６の通信品質は、例えば、アクセスポイント１６ａから送信される報知情報を受信して取得（測定）する。 First, the operation of the handover control unit 36 will be mainly described. The handover control unit 36 determines a handover schedule based on the communication qualities acquired from the first wireless I / F 31 and the second wireless I / F 32 via the wireless information acquisition unit 35, respectively. For example, when a call is made by forming a wireless link with the first wireless communication network 15, the communication quality acquired from the first wireless I / F 31 becomes worse than the handover schedule determination threshold, and the second wireless I / F When the communication quality of F32 is equal to or higher than the handover schedule determination threshold, the handover control unit 36 determines the handover schedule to the second wireless communication network 16, that is, determines the start of handover preparation. The communication quality of the second wireless communication network 16 that is not used for a call is acquired (measured) by receiving broadcast information transmitted from the access point 16a, for example.
　ハンドオーバ制御部３６は、ハンドオーバ予定を決定すると、ハンドオーバ開始までの時間、すなわちハンドオーバ要求情報であるRegistration Request（ＮＥＭＯでは、Binding Update）を送信するまでの時間であるハンドオーバ準備時間Ts(sec)と、現在使用中の無線通信ネットワーク（ここでは、第１無線通信ネットワーク１５）における無線通信装置１１とＨＡ２３との間の上りの絶対遅延時間Tdup1(sec)、ハンドオーバ先の無線通信ネットワーク（ここでは、第２無線通信ネットワーク１６）における無線通信装置１１とＨＡ２３との間の上りの絶対遅延時間Tdup2(sec)および下りの絶対遅延時間Tddn2(sec) と、ハンドオーバ完了後のハンドオーバ先の無線通信ネットワークにおける上りの予測帯域Rbup2(bps) とを取得する。 When the handover control unit 36 determines the handover schedule, the handover preparation time Ts (sec), which is the time until the start of the handover, that is, the time until the Registration Request (Binding Update in NEMO) is transmitted, The uplink absolute delay time Tdup1 (sec) between the wireless communication device 11 and the HA 23 in the wireless communication network currently used (here, the first wireless communication network 15), and the handover destination wireless communication network (here, the first wireless communication network) 2) In the wireless communication network 16), the uplink absolute delay time Tdup2 (sec) and the downlink absolute delay time Tddn2 (sec) between the wireless communication device 11 and the HA 23, and the uplink in the handover destination wireless communication network after the handover is completed. Of the predicted bandwidth Rbup2 (bps).
　そして、ハンドオーバ制御部３６は、これらの取得情報を、所要のハンドオーバ情報として、ハンドオーバの予定決定を示すハンドオーバ予定決定情報を含めて、電話機能部３３に供給する。また、電話機能部３３は、ハンドオーバ制御部３６から取得したハンドオーバ情報のうち、所要のハンドオーバ情報をハンドオーバ予告メッセージとして、ＨＡ２３を介して通信装置１２に送信する。したがって、本実施の形態に係る無線通信装置１１において、ハンドオーバ制御部３６は、ハンドオーバの準備を開始するか否かを決定する決定部、ハンドオーバ準備時間を推定する推定部、および第１無線通信ネットワーク１５および第２無線通信ネットワーク１６におけるそれぞれの遅延時間を計測する計測部を構成する。 Then, the handover control unit 36 supplies the obtained information to the telephone function unit 33 as necessary handover information including handover schedule determination information indicating handover schedule determination. In addition, the telephone function unit 33 transmits the required handover information among the handover information acquired from the handover control unit 36 to the communication apparatus 12 via the HA 23 as a handover advance notice message. Therefore, in radio communication apparatus 11 according to the present embodiment, handover control unit 36 includes a determination unit that determines whether to start preparation for handover, an estimation unit that estimates handover preparation time, and the first radio communication network. 15 and the measurement part which measures each delay time in the 2nd radio | wireless communication network 16 is comprised.
　次に、ハンドオーバ制御部３６による、上記のハンドオーバ準備時間Ts、ハンドオーバ元上り絶対遅延時間Tdup1、ハンドオーバ先上りおよび下り絶対遅延時間Tdup2およびTddn2、並びに、ハンドオーバ先予測帯域Rbup2の取得方法について説明する。 Next, a method for obtaining the handover preparation time Ts, the handover source uplink absolute delay time Tdup1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, and the handover destination predicted bandwidth Rbup2 by the handover control unit 36 will be described.
（ハンドオーバ準備時間Tsの取得方法）
　ハンドオーバ準備時間Tsは、例えば、図４（ａ）および（ｂ）に示すように、通信品質を決定する無線状態(Rs)の単位時間の変化率ΔRs（傾き）に基づいて算出する。ここで、変化率ΔRsは、無線状態がハンドオーバ予定決定閾値を下回ってハンドオーバ予定を決定した時点で計測して取得することもできるが、本実施の形態では、当該通話中において、ハンドオーバの予定決定時点から所定時間前までの変化率平均値ΔRsrmsを取得する。 (How to obtain handover preparation time Ts)
For example, as shown in FIGS. 4A and 4B, the handover preparation time Ts is calculated based on a unit time change rate ΔRs (slope) of the radio state (Rs) for determining communication quality. Here, the rate of change ΔRs can be measured and acquired when the radio state falls below the handover schedule determination threshold and the handover schedule is determined, but in this embodiment, the handover schedule determination is performed during the call. The change rate average value ΔRsrms from the time point to a predetermined time before is acquired.
　このため、ハンドオーバ制御部３６は、下式に従って、現在使用中の無線通信ネットワークにおける無線状態の単位時間（Δｔ）の変化率ΔRs(t)を所定のタイミングで算出して、所定時間前（例えば、２sec前）までの複数の変化率ΔRs(t)をメモリに保持する。そして、ハンドオーバ予定を決定すると、その時点で保持していた所定時間前までの変化率平均値ΔRsrmsを算出する。なお、ここでは、徐々に無線状態が悪化していることを前提とする。
［数１］
　ΔRs(t)＝|{Rs(t)－Rs(t-Δt)}／Δt|
For this reason, the handover control unit 36 calculates the change rate ΔRs (t) of the unit time (Δt) of the radio state in the currently used radio communication network according to the following formula at a predetermined timing, A plurality of change rates ΔRs (t) up to 2 seconds before) are held in the memory. When the handover schedule is determined, the change rate average value ΔRsrms up to a predetermined time held at that time is calculated. Here, it is assumed that the wireless state is gradually getting worse.
[Equation 1]
ΔRs (t) = | {Rs (t) −Rs (t−Δt)} / Δt |
　その後、ハンドオーバ制御部３６は、算出した変化率平均値ΔRsrmsが、予め設定した変化率閾値Rsrefよりも小さいか否かを判定する。その結果、ΔRsrms≦Rsrefの場合、すなわち、無線状態の変化が緩やかな場合には、図４（ａ）に示すように、ハンドオーバ準備時間Tsを、予め設定した標準時間Tref（例えば、５sec）とする。 Thereafter, the handover control unit 36 determines whether or not the calculated change rate average value ΔRsrms is smaller than a preset change rate threshold value Rsref. As a result, in the case of ΔRsrms ≦ Rsref, that is, when the wireless state changes slowly, as shown in FIG. 4A, the handover preparation time Ts is set to a preset standard time Tref (for example, 5 sec). To do.
　これに対し、ΔRsrms＞Rsrefの場合、すなわち、無線状態の変化が急激な場合には、例えば、Ts＝Tref（Rsref／ΔRsrms）、を演算して、変化率ΔRsrmsが大きいほど、ハンドオーバ準備時間Tsを、標準時間Trefよりも短く設定する。図４（ｂ）は、ΔRsrms＞Rsrefの場合で、ハンドオーバ準備時間Tsを、標準時間Trefのほぼ半分の時間（２．５sec）に設定した場合を示す。 On the other hand, when ΔRsrms> Rsref, that is, when the radio state changes rapidly, for example, Ts = Tref (Rsref / ΔRsrms) is calculated, and the higher the rate of change ΔRsrms, the greater the handover preparation time Ts. Is set shorter than the standard time Tref. FIG. 4B shows a case where ΔRsrms> Rsref and the handover preparation time Ts is set to approximately half the standard time Tref (2.5 sec).
（絶対遅延時間Tdup1、Tdup2、Tddn2の取得方法）
　無線通信装置１１とＨＡ２３との間のハンドオーバ元上り絶対遅延時間Tdup1、ハンドオーバ先上りおよび下り絶対遅延時間Tdup2およびTddn2は、例えば、以下に説明する第１～第３の絶対遅延時間取得方法のいずれかによって取得する。 (Acquisition method of absolute delay time Tdup1, Tdup2, Tddn2)
The handover source uplink absolute delay time Tdup1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2 between the wireless communication apparatus 11 and the HA 23 are, for example, any of the first to third absolute delay time acquisition methods described below. Get by.
（ａ）第１の絶対遅延時間取得方法
　ハンドオーバ制御部３６は、ハンドオーバの予定を決定すると、第１無線Ｉ／Ｆ３１および第２無線Ｉ／Ｆ３２を介して、無線通信装置１１と時間同期しているＨＡ２３に対して送信タイムスタンプを有する計測用パケットを送信して、ＨＡ２３から当該送信タイムスタンプとＨＡ２３での受信タイムスタンプ、およびＨＡ２３からの返信タイムスタンプを有する計測用パケットの返信を要求する。これにより、ＨＡ２３から、第１無線通信ネットワーク１５および第２無線通信ネットワーク１６の双方から計測用パケットを送信させる。無線通信装置１１は、ＨＡ２３から送信された計測用パケットを、対応する第１無線Ｉ／Ｆ３１および第２無線Ｉ／Ｆ３２を介してそれぞれ受信し、その受信時刻と計測用パケットのタイムスタンプとから、対応するネットワークの絶対遅延時間Tdup1、Tdup2、Tddn2を計測する。 (A) First Absolute Delay Time Acquisition Method When the handover control unit 36 determines a handover schedule, the handover control unit 36 synchronizes with the radio communication apparatus 11 via the first radio I / F 31 and the second radio I / F 32 in time synchronization. The HA 23 transmits a measurement packet having a transmission time stamp, and requests the HA 23 to return a measurement packet having the transmission time stamp, the reception time stamp at the HA 23, and a return time stamp from the HA 23. Thereby, the measurement packet is transmitted from both the first wireless communication network 15 and the second wireless communication network 16 from the HA 23. The wireless communication device 11 receives the measurement packet transmitted from the HA 23 via the corresponding first wireless I / F 31 and second wireless I / F 32, respectively, and based on the reception time and the time stamp of the measurement packet. Measure absolute delay times Tdup1, Tdup2, and Tddn2 of the corresponding network.
（ｂ）第２の絶対遅延時間取得方法
　ハンドオーバ制御部３６は、ハンドオーバの予定を決定すると、無線通信装置１１から該無線通信装置１１と時間同期しているＨＡ２３に対して、第１無線通信ネットワーク１５および第２無線通信ネットワーク１６の双方から、ＰＩＮＧやＲＴＣＰ等の計測用パケットを送信させ、その返信を受信して、対応するネットワークの絶対遅延時間Tdup1、Tdup2、Tddn2を計測する。 (B) Second Absolute Delay Time Acquisition Method When the handover control unit 36 determines a handover schedule, the handover control unit 36 transmits a first wireless communication network from the wireless communication device 11 to the HA 23 that is time-synchronized with the wireless communication device 11. 15 and the second wireless communication network 16 transmit measurement packets such as PING and RTCP, receive the reply, and measure the absolute delay times Tdup1, Tdup2, and Tddn2 of the corresponding networks.
（c）第３の絶対遅延時間取得方法
　ハンドオーバ制御部３６は、ハンドオーバの予定を決定すると、ＩＥＥＥ８０２．２１において検討されているハンドオーバ技術を利用して、各無線通信ネットワークの絶対遅延時間を取得する。ＩＥＥＥ８０２．２１（Media　Independent　Handover（MIH））では、異種無線通信ネットワーク（ＷｉＦｉ(Wireless Fidelity)、ＷｉＭＡＸ（Worldwide Interoperability for Microwave Access）、携帯電話など）間のハンドオーバ技術として、ハンドオーバを制御する手段（図２では、ハンドオーバ制御部３６）をＭＩＨユーザと定義し、ＭＩＨＦ（MIH Function）がＭＩＨユーザからの要求に基づいて、通信デバイスの無線情報を取得して、ＭＩＨユーザに提供することを考えている。また、ＭＩＨユーザが、自らの端末内のＭＩＨＦを通して、接続しているネットワーク内のインフォメーションサーバから情報を取得することも考えられている。 (C) Third Absolute Delay Time Acquisition Method When the handover control unit 36 determines a handover schedule, the handover control unit 36 acquires the absolute delay time of each wireless communication network by using a handover technique studied in IEEE 802.21. . IEEE 802.21 (Media Independent Handover (MIH)) is a means for controlling handover as a handover technique between different types of wireless communication networks (WiFi (Wireless Fidelity), WiMAX (Worldwide Interoperability for Microwave Access), mobile phones, etc.) (see FIG. 2, the handover control unit 36) is defined as an MIH user, and MIHF (MIH Function) acquires wireless information of a communication device based on a request from the MIH user and provides it to the MIH user. . It is also considered that an MIH user acquires information from an information server in a connected network through MIHF in his / her terminal.
　図５は、この第３の絶対遅延時間取得方法を説明するための図である。図５において、基幹ネットワーク網であるインターネット１８には、遅延時間を計測するために動作する計測用サーバ６１が接続されており、第１無線通信ネットワーク１５には、第１インフォメーションサーバ６２が接続されており、第２無線通信ネットワーク１６には、第２インフォメーションサーバ６３が接続されている。 FIG. 5 is a diagram for explaining the third absolute delay time acquisition method. In FIG. 5, a measurement server 61 that operates to measure delay time is connected to the Internet 18 that is a backbone network, and a first information server 62 is connected to the first wireless communication network 15. A second information server 63 is connected to the second wireless communication network 16.
　第１インフォメーションサーバ６２は、インターネット１８に直接繋がった計測用サーバ６１から基地局１５ａまでの、遅延時間計測の基準とするネットワーク遅延基準時間Tn1と、基地局１５ａから無線通信装置１１までの上下の無線遅延基準時間Trup1、Trdn1を保持する。同様に、第２インフォメーションサーバ６３は、計測用サーバ６１からアクセスポイント１６ａまでのネットワーク遅延基準時間Tn2と、アクセスポイント１６ａから無線通信装置１１までの上下の無線遅延基準時間Trup2、Trdn2を保持する。 The first information server 62 includes a network delay reference time Tn1 as a reference for delay time measurement from the measurement server 61 directly connected to the Internet 18 to the base station 15a, and upper and lower distances from the base station 15a to the wireless communication device 11. Holds radio delay reference times Trup1 and Trdn1. Similarly, the second information server 63 holds the network delay reference time Tn2 from the measurement server 61 to the access point 16a, and the upper and lower radio delay reference times Trup2 and Trdn2 from the access point 16a to the wireless communication device 11.
　ここで、ネットワーク遅延基準時間Tn1およびTn2は、基地局１５ａと計測用サーバ６１との間、およびアクセスポイント１６ａと計測用サーバ６１との間で、それぞれパケット（ＰＩＮＧやＲＴＣＰなど）を送受信して往復時間を測り、その往復時間を１／２して取得される。 Here, the network delay reference times Tn1 and Tn2 are transmitted and received between the base station 15a and the measurement server 61, and between the access point 16a and the measurement server 61, respectively (such as PING and RTCP). The round trip time is measured, and the round trip time is halved.
　また、第１無線通信ネットワーク１５における上下の無線遅延基準時間Trup1、Trdn1は、基地局１５ａから無線通信装置１１へパケットを送り、パケットを受信した無線通信装置１１は受信した時間を記録して送り返すことで、基地局１５ａと無線通信装置１１との間で送受信した時間に基づいて、上り・下りのそれぞれの遅延時間が計算される。 In addition, the upper and lower radio delay reference times Trup1 and Trdn1 in the first radio communication network 15 send a packet from the base station 15a to the radio communication device 11, and the radio communication device 11 that has received the packet records and returns the received time. Thus, the respective uplink and downlink delay times are calculated based on the times transmitted and received between the base station 15a and the wireless communication device 11.
　同様に、第２無線通信ネットワーク１６における上下の無線遅延基準時間Trup2、Trdn2は、アクセスポイント１６ａから無線通信装置１１へパケットを送り、パケットを受信した無線通信装置１１は受信した時間を記録して送り返すことで、アクセスポイント１６ａと無線通信装置１１との間で送受信した時間に基づいて、上り・下りのそれぞれの遅延時間が計算される。なお、Trup1,Trup2は上りの無線遅延基準時間を示しており、Trdn1,Trdn2は下りの無線遅延基準時間を示している。 Similarly, the upper and lower radio delay reference times Trup2 and Trdn2 in the second radio communication network 16 send a packet from the access point 16a to the radio communication device 11, and the radio communication device 11 that receives the packet records the received time. By sending it back, each of the uplink and downlink delay times is calculated based on the time transmitted and received between the access point 16a and the wireless communication device 11. Trup1 and Trup2 indicate uplink radio delay reference times, and Trdn1 and Trdn2 indicate downlink radio delay reference times.
　無線通信装置１１のハンドオーバ制御部３６は、ハンドオーバ元である第１無線通信ネットワーク１５への接続時に、当該第１無線通信ネットワーク１５に接続されている第１インフォメーションサーバ６２からＭＩＨＦを介してネットワーク遅延基準時間Tn1と無線遅延基準時間Trdn1,Trup1とを取得する。また、ハンドオーバ制御部３６は、遅延時間を測りたい相手先（ここでは、ＨＡ２３）とパケットの送受信を行い、相手と自らの無線通信装置１１との間の往復時間(Tn3+Trdn3+Tn3+Trup3)を計測する。そして、ハンドオーバ制御部３６は、この値から、以下のようにして、ＨＡ２３とインターネット１８との間の片道の遅延時間(Tn3-Tn1)を求めて、無線通信装置１１とＨＡ２３との間のハンドオーバ元上り絶対遅延時間Tdup1に相当するTn3+Trup3を計算する。 When connecting to the first wireless communication network 15 that is the handover source, the handover control unit 36 of the wireless communication device 11 sends a network delay from the first information server 62 connected to the first wireless communication network 15 via the MIHF. The reference time Tn1 and the radio delay reference times Trdn1 and Trup1 are acquired. Further, the handover control unit 36 transmits / receives a packet to / from the other party (here, the HA 23) whose delay time is to be measured, and the round-trip time (Tn3 + Trdn3 + Tn3 + Trup3) between the other party and its own wireless communication device 11 ). Then, the handover controller 36 obtains a one-way delay time (Tn3-Tn1) between the HA 23 and the Internet 18 from this value as follows, and performs a handover between the wireless communication apparatus 11 and the HA 23. Tn3 + Trup3 corresponding to the original upstream absolute delay time Tdup1 is calculated.
［数２］
　Tn3-Tn1={(Tn3+Trdn3+Tn3+Trup3)-(Tn1+Trdn1+Tn1+Trup1)}/2
　Tdup1=Tn3+Trup3=Tn1+Trup1+(Tn3-Tn1)
[Equation 2]
Tn3-Tn1 = {(Tn3 + Trdn3 + Tn3 + Trup3)-(Tn1 + Trdn1 + Tn1 + Trup1)} / 2
Tdup1 = Tn3 + Trup3 = Tn1 + Trup1 + (Tn3-Tn1)
　なお、無線通信装置１１とＨＡ２３との間のハンドオーバ元下り絶対遅延時間Tddn1に相当するTn3+Trdn3は、Tn3+Trdn3=Tn1+Trdn1+(Tn3-Tn1)、により算出することができる。 Note that Tn3 + Trdn3 corresponding to the handover source absolute downlink delay time Tddn1 between the wireless communication apparatus 11 and the HA 23 can be calculated by Tn3 + Trdn3 = Tn1 + Trdn1 + (Tn3-Tn1).
　また、ハンドオーバ制御部３６は、ハンドオーバ先のネットワーク遅延基準時間Tn2および無線遅延基準時間Trup2、Trdn2を取得する。このため、現在接続している第１無線通信ネットワーク１５の第１インフォメーションサーバ６２を経由して、ハンドオーバ先の第２無線通信ネットワーク１６の第２インフォメーションサーバ６３に、当該無線通信装置１１の位置情報を送信して、ネットワーク遅延基準時間Tn2および無線遅延基準時間Trup2、Trdn2の返信を要求する。これにより、第２インフォメーションサーバ６３は、位置情報と各アクセスポイントの接続ユーザ数とを考慮して、接続されると思われるアクセスポイント１６ａのネットワーク遅延基準時間Tn2および無線遅延基準時間Trup2,Trdn2を、第１インフォメーションサーバ６２を経由して無線通信装置１１へ返信する。 Further, the handover control unit 36 acquires the network delay reference time Tn2 and the radio delay reference times Trup2 and Trdn2 of the handover destination. Therefore, the location information of the wireless communication device 11 is transmitted to the second information server 63 of the second wireless communication network 16 that is the handover destination via the first information server 62 of the first wireless communication network 15 that is currently connected. To request a reply of the network delay reference time Tn2 and the radio delay reference times Trup2 and Trdn2. As a result, the second information server 63 determines the network delay reference time Tn2 and the radio delay reference times Trup2 and Trdn2 of the access point 16a that is considered to be connected in consideration of the position information and the number of connected users of each access point. The response is made to the wireless communication device 11 via the first information server 62.
　ハンドオーバ制御部３６は、第２インフォメーションサーバ６３から返信されるハンドオーバ先のネットワーク遅延基準時間Tn2および無線遅延基準時間Trup2,Trdn2を受信し、その取得情報と算出した(Tn3-Tn1)とを用いて、以下のようにして、無線通信装置１１とＨＡ２３との間のハンドオーバ先上り絶対遅延時間Tdup2に相当するTn4+Trup4と、下り絶対遅延時間Tddn2に相当するTn4+Trdn4とを計算する。 The handover controller 36 receives the handover destination network delay reference time Tn2 and the radio delay reference times Trup2, Trdn2 returned from the second information server 63, and uses the obtained information and the calculated (Tn3-Tn1). In the following manner, Tn4 + Trup4 corresponding to the handover destination uplink absolute delay time Tdup2 and Tn4 + Trdn4 corresponding to the downlink absolute delay time Tddn2 between the wireless communication apparatus 11 and the HA 23 are calculated.
［数３］
　Tdup2=Tn4+Trup4=(Tn2+Trup2)+(Tn3-Tn1)
　Tddn2=Tn4+Trdn4=(Tn2+Trdn2)+(Tn3-Tn1)
[Equation 3]
Tdup2 = Tn4 + Trup4 = (Tn2 + Trup2) + (Tn3-Tn1)
Tddn2 = Tn4 + Trdn4 = (Tn2 + Trdn2) + (Tn3-Tn1)
　ハンドオーバ制御部３６は、上記の第１～第３の絶対遅延時間取得方法のいずれかによって取得した絶対遅延時間Tdup1、Tdup2、Tddn2を、無線通信ネットワーク毎に、ハンドオーバ制御部３６内のメモリ（図示せず）に記憶する。 The handover control unit 36 stores the absolute delay times Tdup1, Tdup2, and Tddn2 acquired by any of the first to third absolute delay time acquisition methods in the memory (see FIG. (Not shown).
（ハンドオーバ先予測帯域Rbup2の取得方法）
　ハンドオーバ先の上りの予測帯域Rbup2は、ハンドオーバ完了後のハンドオーバ先の無線通信ネットワークにおける上りの無線状態を予測して取得する。このため、ハンドオーバ制御部３６には、例えば、図６に示すような無線状態（通信品質）とスループット（予測帯域）との変換テーブルを予め記憶しておく。ハンドオーバ制御部３６は、例えば、ハンドオーバ予定決定時点におけるハンドオーバ先の無線状況と、その時点から所定時間前のハンドオーバ先の無線状況とに基づいて、ハンドオーバ完了時のハンドオーバ先の無線状態を線形に予測し、その予測した無線状態に基づいて、図６の変換テーブルから、ハンドオーバ完了時点のハンドオーバ先予測帯域Rbup2を取得する。ここで、ハンドオーバ完了時点は、ハンドオーバ予定決定時点から、ハンドオーバ準備時間Tsと、ハンドオーバ先の無線通信ネットワーク（ここでは、第２無線通信ネットワーク１６）におけるＨＡ２３と無線通信装置１１との間の往復の絶対遅延時間(Trup2+Trdn2)とを加算した時点とする。 (Acquisition method of handover destination predicted bandwidth Rbup2)
The uplink predicted bandwidth Rbup2 of the handover destination is obtained by predicting the uplink radio state in the handover destination radio communication network after completion of the handover. For this reason, the handover control unit 36 stores, for example, a conversion table between the wireless state (communication quality) and the throughput (predicted bandwidth) as shown in FIG. For example, the handover control unit 36 linearly predicts the handover destination radio status at the completion of the handover based on the handover destination radio status at the time when the handover schedule is determined and the handover destination radio status a predetermined time before that time. Then, based on the predicted radio condition, the handover destination predicted bandwidth Rbup2 at the time of handover completion is acquired from the conversion table of FIG. Here, the handover completion time point is the round-trip time between the HA 23 and the wireless communication device 11 in the handover destination wireless communication network (here, the second wireless communication network 16) from the handover schedule determination time point. The absolute delay time (Trup2 + Trdn2) is added.
　以上のようにして、ハンドオーバ制御部３６は、ハンドオーバ準備時間Ts、ハンドオーバ元上り絶対遅延時間Tdup1、ハンドオーバ先上りおよび下り絶対遅延時間Tdup2およびTddn2、並びに、ハンドオーバ先予測帯域Rbup2を取得して、それらの取得情報を電話機能部３３に供給する。 As described above, the handover control unit 36 acquires the handover preparation time Ts, the handover source uplink absolute delay time Tdup1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, and the handover destination predicted bandwidth Rbup2. Is acquired to the telephone function unit 33.
　また、ハンドオーバ制御部３６は、ハンドオーバ予定を決定した場合は、ハンドオーバ処理を実行する。 Further, when the handover control unit 36 determines a handover schedule, the handover control unit 36 executes a handover process.
　図７は、無線通信装置１１とＨＡ２３との間のハンドオーバ処理を説明するためのシーケンス図である。図７に示すように、無線通信装置（ＭＮ）１１のハンドオーバ制御部３６は、ハンドオーバ予定を決定すると、通信処理部３４を制御して、第２無線Ｉ／Ｆ３２を第２無線通信ネットワーク１６に接続する。その後、ハンドオーバ制御部３６は、ハンドオーバ準備時間Tsが経過した時点で、ハンドオーバ先の第２無線通信ネットワーク１６を介してＨＡ２３にハンドオーバ要求情報であるRegistration Request（ＮＥＭＯでは、Binding Update）を送信する。なお、ハンドオーバ制御部３６は、ＨＡ２３にハンドオーバ要求情報を送信すると、その旨を示すハンドオーバ予定通知を、ハンドオーバ情報として電話機能部３３に送信する。 FIG. 7 is a sequence diagram for explaining a handover process between the wireless communication apparatus 11 and the HA 23. As illustrated in FIG. 7, when the handover control unit 36 of the wireless communication device (MN) 11 determines a handover schedule, the handover control unit 36 controls the communication processing unit 34 to transfer the second wireless I / F 32 to the second wireless communication network 16. Connecting. Thereafter, when the handover preparation time Ts elapses, the handover control unit 36 transmits a Registration Request (in NEMO, Binding Update) to the HA 23 via the second wireless communication network 16 that is the handover destination. When the handover control unit 36 transmits the handover request information to the HA 23, the handover control unit 36 transmits a handover schedule notification indicating the fact to the telephone function unit 33 as the handover information.
　ＨＡ２３は、ハンドオーバ要求情報を受信すると、ハンドオーバ先のＩＰアドレスを気付けアドレス（第２無線ＣｏＡ）として登録して、ハンドオーバ完了情報であるRegistration Reply（ＮＥＭＯでは、Binding Acknowledge）を、第２無線通信ネットワーク１６を介して無線通信装置１１に返信する。なお、ＨＡ２３は、無線通信装置１１に対して一つの気付けアドレスのみを登録する。したがって、ハンドオーバ先の気付けアドレス（第２無線ＣｏＡ）は、既に登録されているハンドオーバ元の気付けアドレス（第１無線ＣｏＡ）に上書きして登録する。ＨＡ２３は、ハンドオーバ先の気付けアドレスを登録すると、その時点から、登録した気付けアドレス（第２無線ＣｏＡ）からのパケットのみを受け付け、以前の気付けアドレス（第１無線ＣｏＡ）が送信元であるパケットは受け付けない。 Upon receipt of the handover request information, the HA 23 registers the IP address of the handover destination as a care-of address (second wireless CoA), and registers Registration Reply (Binding Acknowledge in NEMO) as the second wireless communication network. 16 is sent back to the wireless communication apparatus 11 via 16. Note that the HA 23 registers only one care-of address with the wireless communication device 11. Therefore, the care-of address of the handover destination (second radio CoA) is registered by overwriting the care-of address of the handover source (first radio CoA) already registered. When the care-of address of the handover destination is registered, the HA 23 accepts only the packet from the registered care-of address (second wireless CoA) from that point, and the packet whose source is the previous care-of address (first wireless CoA) Not accepted.
　その後、ハンドオーバ制御部３６は、ＨＡ２３から返信されるハンドオーバ完了情報であるRegistration Reply（ＮＥＭＯでは、Binding Acknowledge）を受信すると、ハンドオーバ先の第２無線通信ネットワーク１６によりパケットの送受信を開始するとともに、通信処理部３４を制御して、第１無線Ｉ／Ｆ３１とハンドオーバ元の第１無線通信ネットワーク１５との接続を切断する。なお、ハンドオーバ制御部３６は、ＨＡ２３からハンドオーバ完了情報を受信すると、その旨を示すハンドオーバ完了通知を、ハンドオーバ情報として電話機能部３３に送信する。 Thereafter, upon receiving RegistrationRegReply (Binding Acknowledge in NEMO) as handover completion information sent back from the HA 23, the handover control unit 36 starts transmission / reception of packets by the second wireless communication network 16 as the handover destination, and performs communication. The processing unit 34 is controlled to disconnect the connection between the first wireless I / F 31 and the first wireless communication network 15 that is the handover source. When the handover control unit 36 receives the handover completion information from the HA 23, the handover control unit 36 transmits a handover completion notification indicating the fact to the telephone function unit 33 as the handover information.
　図７から明らかなように、ＨＡ２３は、ハンドオーバ先のＩＰアドレスを気付けアドレス（第２無線ＣｏＡ）として登録した後は、ハンドオーバ元からの送信パケットは受け付けない。このため、ハンドオーバ元の第１無線通信ネットワーク１５を介して、無線通信装置１１からＨＡ２３に送信されたパケットのうち、ハンドオーバ要求情報がＨＡ２３に届いた後に、ＨＡ２３に到着するパケットはロストすることになる。 As is apparent from FIG. 7, the HA 23 does not accept a transmission packet from the handover source after registering the IP address of the handover destination as the care-of address (second wireless CoA). For this reason, of the packets transmitted from the wireless communication device 11 to the HA 23 via the first wireless communication network 15 that is the handover source, the packet that arrives at the HA 23 after the handover request information reaches the HA 23 is lost. Become.
　図８は、この場合のパケットロスの発生を説明するための図である。ここでは、便宜上、ＮＥＭＯを例にとって説明する。図８に示すように、ＨＡ２３は、無線通信装置（ＭＮ）１１からBinding Updateを受信して、そのハンドオーバ先のＩＰアドレスを気付けアドレス（第２無線ＣｏＡ）として登録すると、その後は、ハンドオーバ先からのパケットのみを受け付けることになる。 FIG. 8 is a diagram for explaining the occurrence of packet loss in this case. Here, for convenience, NEMO will be described as an example. As shown in FIG. 8, the HA 23 receives the Binding Update from the wireless communication device (MN) 11 and registers the handover destination IP address as the care-of address (second wireless CoA). Only the packet will be accepted.
　このため、ハンドオーバ元の上りの絶対遅延時間Tdup1が、ハンドオーバ先の上りの絶対遅延時間Tdup2よりも長い場合は、無線通信装置（ＭＮ）１１がBinding Updateを送信した時点よりも、Tsttlow=Tdup1-Tdup2、手前の時点Twsから、無線通信装置（ＭＮ）１１がＨＡ２３からBinding Ackを受信する時点までに、ハンドオーバ元から送信されたパケットは、ロストすることになる。このパケットのロスト期間Tlostは、Tlost=Tdup1+Tddn2、となる。また、ＨＡ２３は、Binding Updateを受信してから、ハンドオーバ先からのパケットが到着するまでの期間、すなわち、Tdup2+Tddn2、の期間はパケットを受信しないことになる。なお、図８において、一点鎖線はハンドオーバ前のパケットの流れを示している。 For this reason, when the absolute delay time Tdup1 of the handover source uplink is longer than the absolute delay time Tdup2 of the handover destination uplink, Tsttlow = Tdup1- is greater than the time when the wireless communication device (MN) 11 transmits Binding Update. From Tdup2, the previous time point Tws to the time point when the wireless communication device (MN) 11 receives Binding Ack from the HA 23, the packet transmitted from the handover source is lost. The lost period Tlost of this packet is Tlost = Tdup1 + Tddn2. In addition, the HA 23 does not receive a packet during a period from reception of Binding-Update until arrival of a packet from the handover destination, that is, a period of Tdup2 + Tddn2. In FIG. 8, the alternate long and short dash line indicates the packet flow before the handover.
　そこで、本実施の形態に係る無線通信装置１１は、電話機能部３３において、ハンドオーバ制御部３６からのハンドオーバ情報に基づいて、ハンドオーバによってロストすると思われる送信データを電話機能部３３内の送信バッファ５７に蓄積して、ハンドオーバ完了後に送信するようにデータの送信を制御する。 Therefore, in the radio communication apparatus 11 according to the present embodiment, in the telephone function unit 33, based on the handover information from the handover control unit 36, the transmission data 57 that is supposed to be lost due to handover is transmitted to the transmission buffer 57 in the telephone function unit 33. The transmission of data is controlled so as to be transmitted after the handover is completed.
　次に、電話機能部３３によるハンドオーバ時のデータ送信処理について説明する。 Next, data transmission processing at the time of handover by the telephone function unit 33 will be described.
　図９は、電話機能部３３によるハンドオーバ時のデータ送信処理の概要を説明するための図である。上述したように、無線通信装置（ＭＮ）１１から送信されるパケットは、Binding Updateが送信される時点よりもTsttlow手前の時点Twsから、ロスト期間Tlostに相当する期間Ａでロストする。このため、この期間Ａにおいては、電話機能部３３は、送信データの符号化ビットレートを下げるとともに、データを送信しながらそのコピーを送信バッファ５７に蓄積する。 FIG. 9 is a diagram for explaining an outline of data transmission processing at the time of handover by the telephone function unit 33. As described above, the packet transmitted from the wireless communication device (MN) 11 is lost in the period A corresponding to the lost period Tlost from the time Tws before Tsttlow before the time when the Binding Update is transmitted. For this reason, during this period A, the telephone function unit 33 lowers the encoding bit rate of the transmission data and accumulates a copy thereof in the transmission buffer 57 while transmitting the data.
　その後、電話機能部３３は、ハンドオーバ先からのパケットの送信が開始されたら、新しいデータを送信バッファ５７内に蓄積しながら、送信バッファ５７内のパケットが０となるまで、送信バッファ５７内のデータを速く送信する（期間Ｂ）。その後、通信が終了するまで、あるいは、次のハンドオーバ予定による期間Ａが開始されるまでは、電話機能部３３は、送信データを通常の符号化ビットレートでエンコードして、送信バッファ５７に蓄積することなく送信する（期間Ｃ）。 After that, when transmission of a packet from the handover destination is started, the telephone function unit 33 accumulates new data in the transmission buffer 57 and keeps data in the transmission buffer 57 until the packet in the transmission buffer 57 becomes zero. Is transmitted quickly (period B). Thereafter, the telephone function unit 33 encodes the transmission data at the normal encoding bit rate and stores it in the transmission buffer 57 until the communication is completed or until the period A by the next handover schedule is started. (Period C).
　図１０は、電話機能部３３の送信制御部５６によるハンドオーバ時の動作を示すフローチャートである。以下、図１０に示すフローチャートを参照しながら、電話機能部３３によるハンドオーバ時のデータ送信処理について、さらに詳細に説明する。 FIG. 10 is a flowchart showing the operation at the time of handover by the transmission control unit 56 of the telephone function unit 33. Hereinafter, the data transmission process at the time of handover by the telephone function unit 33 will be described in more detail with reference to the flowchart shown in FIG.
　電話機能部３３のハンドオーバ情報取得部５５は、ハンドオーバ制御部３６からのハンドオーバ情報を一定間隔毎に監視する。その結果、ハンドオーバ予定決定情報を取得した場合は、さらに、ハンドオーバ制御部３６からの所要のハンドオーバ情報である、ハンドオーバ準備時間Ts、ハンドオーバ元上り絶対遅延時間Tdup1、ハンドオーバ先上りおよび下り絶対遅延時間Tdup2およびTddn2、ハンドオーバ先予測帯域Rbup2を取得して、その取得した所要のハンドオーバ情報を送信制御部５６に供給する。その後、ハンドオーバ情報取得部５５は、ハンドオーバ制御部３６からのハンドオーバ予定通知およびハンドオーバ完了通知を一定間隔毎に監視して、それらの受信情報を送信制御部５６に供給するとともに、ハンドオーバ完了通知を取得した場合は、ハンドオーバの予定があるか否かの情報取得に戻る。 The handover information acquisition unit 55 of the telephone function unit 33 monitors the handover information from the handover control unit 36 at regular intervals. As a result, when the handover schedule determination information is acquired, the handover preparation time Ts, the handover source uplink absolute delay time Tdup1, the handover destination uplink and downlink absolute delay time Tdup2 are further required handover information from the handover control unit 36. And Tddn2 and handover destination predicted bandwidth Rbup2 are acquired, and the acquired required handover information is supplied to the transmission control unit 56. Thereafter, the handover information acquisition unit 55 monitors the handover schedule notification and the handover completion notification from the handover control unit 36 at regular intervals, supplies the received information to the transmission control unit 56, and acquires the handover completion notification. If so, the process returns to obtaining information on whether or not there is a handover schedule.
　送信制御部５６は、ハンドオーバ情報取得部５５からハンドオーバ情報を取得すると、その取得情報のうち、ハンドオーバ先予測帯域Rbup2の情報を除くハンドオーバ情報を、通信装置１２に送信する。また、送信制御部５６は、ハンドオーバ情報を取得すると、先ず、パケットロスが生じる期間Ａ（図８参照）の開始時間Twsである送信バッファ５７へのデータ蓄積開始時間と、その際の符号化ビットレートR1とを算出する（ステップＳ１１）。 When the transmission control unit 56 acquires the handover information from the handover information acquisition unit 55, the transmission control unit 56 transmits, to the communication device 12, handover information excluding information on the handover destination predicted band Rbup2 among the acquired information. When the transmission control unit 56 acquires the handover information, first, the data storage start time in the transmission buffer 57, which is the start time Tws of the period A (see FIG. 8) in which the packet loss occurs, and the encoded bit at that time The rate R1 is calculated (step S11).
　ここで、データ蓄積開始時間Twsは、取得したTs、Tdup1、Tdup2から、Tsttlow=Tdup1-Tdup2、として、Tws=Ts-Tsttlow、により算出する。また、符号化ビットレートR1は、取得したRbup2(bps)、通信装置１２のハンドオーバ後の標準再生速度Vnに対する再生速度Vf (sec/sec)、送信バッファ５７の最大容量Sbf(bit)、ロスト期間Tlost(sec)、標準の符号化ビットレートRn(bps)、とするとき、（i）Sbf/ Tlost、（ii）Rbup2/Vf、のうち、小さい方を上限として、取り得る符号化ビットレートの最大値を選択する。なお、ここで選択する符号化ビットレートは、帯域の変動等を考慮して、多少のマージンを持たせて、より低い符号化ビットレートを選択するようにしてもよい。また、ハンドオーバ後の再生速度Vfは、例えば、標準再生速度Vnの１．２５倍と予め設定して、両者で保持するか、あるいは通信装置１２から無線通信装置１１に事前に通知する。 Here, the data accumulation start time Tws is calculated from the acquired Ts, Tdup1, and Tdup2 as Tsttlow = Tdup1-Tdup2 and Tws = Ts-Tsttlow. The encoding bit rate R1 is obtained Rbup2 (bps), the reproduction speed VfV (sec / sec) with respect to the standard reproduction speed Vn after the handover of the communication device 12, the maximum capacity Sbf (bit) of the transmission buffer 57, the lost period When Tlost (sec) is the standard encoding bit rate Rn (bps), (i) Sbf / Tlost and (ii) Rbup2 / Vf Select the maximum value. It should be noted that the encoding bit rate selected here may be set to a lower encoding bit rate with some margin in consideration of band fluctuations and the like. Further, the reproduction speed Vf after the handover is set in advance as 1.25 times the standard reproduction speed Vn, for example, and is held by both, or notified from the communication apparatus 12 to the wireless communication apparatus 11 in advance.
　その後、送信制御部５６は、パケット蓄積開始時間Twsまで待機し（ステップＳ１２）、パケット蓄積開始時間Twsに達すると（期間Ａの開始）、エンコーダ４４に対して、送信データの符号化ビットレートを算出した符号化ビットレートR1まで下げるように指示する（ステップＳ１３）。また、送信制御部５６は、エンコーダ４４から受け取った送信データを、そのままパケット送信部４５に渡しつつ、当該送信データをコピーして送信バッファ５７に蓄積する（ステップＳ１４）。なお、その際、送信データ中の一定（例えば、500msec）以上の長さの無音部分は、上記の一定の長さまで無音データを圧縮する。 Thereafter, the transmission control unit 56 waits until the packet accumulation start time Tws (step S12). When the packet accumulation start time Tws is reached (start of period A), the transmission control unit 56 sets the encoding bit rate of the transmission data to the encoder 44. An instruction is given to lower the calculated encoding bit rate R1 (step S13). Also, the transmission control unit 56 copies the transmission data received from the encoder 44 to the packet transmission unit 45 as it is, and accumulates it in the transmission buffer 57 (step S14). At that time, the silence data having a length of a certain length (for example, 500 msec) or more in the transmission data is compressed to the above-mentioned length.
　上記のステップＳ１４の処理は、ＨＡ２３からのハンドオーバ完了情報を受信するまで行う（ステップＳ１５）。その後、ハンドオーバ完了情報を受信すると（Ｓ１５のYes、期間Ｂの開始）、送信制御部５６は、そのハンドオーバ完了情報を通信装置１２に送信するとともに、エンコーダ４４から受け取った送信データをパケット送信部４５に渡さずに、送信バッファ５７に蓄積しながら、送信バッファ５７に蓄積されているデータ（パケット）を古いものから、帯域に合わせてパケット送信部４５に高速に渡して、通信装置１２に送信する（ステップＳ１６）。 The processing in step S14 is performed until handover completion information is received from the HA 23 (step S15). Thereafter, when handover completion information is received (Yes in S15, start of period B), the transmission control unit 56 transmits the handover completion information to the communication device 12, and transmits the transmission data received from the encoder 44 to the packet transmission unit 45. The data (packet) stored in the transmission buffer 57 is transferred from the oldest to the packet transmission unit 45 at a high speed according to the band and transmitted to the communication device 12 while being stored in the transmission buffer 57 without being passed to (Step S16).
　送信制御部５６は、送信バッファ５７内のパケット数を監視する（ステップＳ１７）。その結果、送信バッファ５７内のパケットが０になると（Ｓ１７のYes、期間Ｃの開始）、送信制御部５６は、エンコーダ４４に符号化ビットレートを元に戻すように指示するとともに（ステップＳ１８）、エンコーダ４４からの送信データを送信バッファ５７に蓄積することなく、パケット送信部４５に渡して、通信装置１２に送信する（ステップＳ１９）。 The transmission control unit 56 monitors the number of packets in the transmission buffer 57 (step S17). As a result, when the packet in the transmission buffer 57 becomes 0 (Yes in S17, start of period C), the transmission control unit 56 instructs the encoder 44 to restore the encoding bit rate (step S18). The transmission data from the encoder 44 is transferred to the packet transmission unit 45 without being stored in the transmission buffer 57 and transmitted to the communication device 12 (step S19).
　図１１は、本実施の形態に係る無線通信装置１１がハンドオーバ時に送信制御を行った場合の通信装置１２との間における送受信パケットの状態を示す図である。また、図１２は、図１１との比較のために、ハンドオーバ時に上記の送信制御を行わなかった場合の無線通信装置と通信装置１２との間における送受信パケットの状態を示す図である。図１１および図１２において、（ａ）～（ｃ）は、通信装置１２における受信パケットシーケンス番号、単位時間の受信パケット数、単位時間の受信データ量（byte）をそれぞれ示し、（ｄ）は、無線通信装置１１による送信データの符号化ビットレート（bps）を示す。 FIG. 11 is a diagram illustrating a state of a transmission / reception packet with the communication device 12 when the wireless communication device 11 according to the present embodiment performs transmission control at the time of handover. FIG. 12 is a diagram illustrating a state of transmission / reception packets between the wireless communication apparatus and the communication apparatus 12 when the above transmission control is not performed at the time of handover for comparison with FIG. 11 and 12, (a) to (c) respectively indicate the received packet sequence number, the number of received packets per unit time, and the received data amount (byte) per unit time in the communication device 12, and (d) The encoding bit rate (bps) of the transmission data by the radio | wireless communication apparatus 11 is shown.
　図１１および図１２の比較から明らかなように、本実施の形態に係る無線通信装置（ＭＮ）１１は、ハンドオーバ時にロストするであろう送信パケットを、無線通信装置１１側で蓄積し、その蓄積したパケットをハンドオーバ後に送信するので、図１２（ａ）では生じていたパケットのロストが、図１１（ａ）では生じない。したがって、ハンドオーバ時でも、通信装置（ＣＮ）１２側では文章の連続性を保つことができるので、音声を聞くユーザに違和感を与えることもない。 As is clear from the comparison between FIG. 11 and FIG. 12, the radio communication apparatus (MN) 11 according to the present embodiment accumulates transmission packets that will be lost at the time of handover on the radio communication apparatus 11 side and accumulates the transmission packets. Since the transmitted packet is transmitted after the handover, the lost packet that occurred in FIG. 12A does not occur in FIG. Therefore, the continuity of the text can be maintained on the communication device (CN) 12 side even at the time of handover, so that the user who listens to the voice does not feel uncomfortable.
　また、図１２（ｄ）では、送信データの符号化ビットレートは一定であるが、本実施の形態に係る無線通信装置（ＭＮ）１１は、図１１（ｄ）に示すように、パケットを蓄積している間は、符号化ビットレートを落としている。したがって、その後、蓄積されたパケットを、限られた帯域の中で滞留を起すことなく、通常より多く送信することができる。これにより、受信側の通信装置（ＣＮ）１２では、図１１（ｂ）および（ｃ）に示す通常よりも多く受信されるパケットを、通常よりも高速に再生することで、本来の絶対遅延での再生に戻すことができる。また、無線通信装置（ＭＮ）１１で、蓄積するパケットを無音圧縮することにより、全体的なデータ容量を低減でき、より速く蓄積したパケットを送信することができる。 In FIG. 12 (d), the encoding bit rate of transmission data is constant, but the wireless communication apparatus (MN) 11 according to the present embodiment accumulates packets as shown in FIG. 11 (d). During this time, the encoding bit rate is reduced. Therefore, thereafter, the accumulated packets can be transmitted more than usual without causing stagnation in a limited band. As a result, the receiving side communication device (CN) 12 reproduces packets received more than usual shown in FIGS. 11B and 11C at a higher speed than usual, thereby achieving the original absolute delay. Can return to playback. In addition, the wireless communication apparatus (MN) 11 can silently compress the stored packets, thereby reducing the overall data capacity and transmitting the stored packets faster.
　次に、図１に示した通信装置（ＣＮ）１２について説明する。 Next, the communication device (CN) 12 shown in FIG. 1 will be described.
　図１３は、通信装置（ＣＮ）１２の概略構成を示す機能ブロック図である。通信装置１２は、図示しないインターネットサービスプロバイダを介してインターネット１８に接続するネットワークＩ／Ｆ（インターフェース）８１と、ネットワークへの接続を制御する通信処理部８２と、ＶｏＩＰのアプリケーションを実行する電話機能部８３と、を有する。 FIG. 13 is a functional block diagram showing a schematic configuration of the communication device (CN) 12. The communication device 12 includes a network I / F (interface) 81 that connects to the Internet 18 via an Internet service provider (not shown), a communication processing unit 82 that controls connection to the network, and a telephone function unit that executes VoIP applications. 83.
　通信処理部８２は、ネットワークＩ／Ｆ８１のインターネット１８への接続を制御して、電話機能部８３と無線通信装置１１との間の通信を実行する。 The communication processing unit 82 controls the connection of the network I / F 81 to the Internet 18 and executes communication between the telephone function unit 83 and the wireless communication device 11.
　図１４は、図１３に示した通信装置１２の電話機能部８３の概略構成を示す機能ブロック図である。電話機能部８３は、例えばソフトフォンからなり、公知のソフトフォンの構成と同様に、ボタン入力部１０１、画面表示部１０２、マイク１０３、エンコーダ１０４、パケット送信部１０５、パケット受信部１０６、ジッタバッファ１０７、デコーダ１０８、スピーカ１０９、ジッタバッファ監視部１１０、ジッタバッファ制御部１１１、ＳＩＰ制御部１１２、および全体の動作を制御する全体制御部１１３を有する。なお、マイク１０３およびスピーカ１０９は、例えば、図１に示したように送受話器１２ａで構成される。 FIG. 14 is a functional block diagram showing a schematic configuration of the telephone function unit 83 of the communication device 12 shown in FIG. The telephone function unit 83 includes, for example, a soft phone, and has a button input unit 101, a screen display unit 102, a microphone 103, an encoder 104, a packet transmission unit 105, a packet reception unit 106, a jitter buffer, as in the configuration of a known soft phone. 107, a decoder 108, a speaker 109, a jitter buffer monitoring unit 110, a jitter buffer control unit 111, a SIP control unit 112, and an overall control unit 113 that controls the overall operation. Note that the microphone 103 and the speaker 109 are constituted by, for example, a handset 12a as shown in FIG.
　全体制御部１１３は、ボタン入力部１０１や画面表示部１０２を介して、ユーザの操作情報を取得し、その取得情報に基づいて全体の動作を制御する。また、ＳＩＰ制御部１１２は、通話の開始や終了のＳＩＰの手続きを制御する。通話中において、マイク１０３から取得された音声データは、エンコーダ１０４でエンコードされ、そのエンコードされたデータは、パケット送信部１０５からパケットに入れられて、通信処理部８２およびネットワークＩ／Ｆ８１を経て無線通信装置１１へ送信される。 The overall control unit 113 acquires user operation information via the button input unit 101 and the screen display unit 102, and controls the overall operation based on the acquired information. The SIP control unit 112 also controls SIP procedures for starting and ending a call. During a call, the audio data acquired from the microphone 103 is encoded by the encoder 104, and the encoded data is put into a packet from the packet transmission unit 105 and wirelessly transmitted through the communication processing unit 82 and the network I / F 81. It is transmitted to the communication device 11.
　また、通信処理部８２を経てパケット受信部１０６で受信された無線通信装置１１からのパケットは、ジッタバッファ１０７に一旦取り込まれてから読み出され、その読み出されたパケットは、デコーダ１０８でペイロード部分がデコードされて、スピーカ１０９から再生音声として出力される。なお、ジッタバッファ１０７のパケットの受信状況や、ジッタバッファ１０７内のパケット数（データ量）の状態は、ジッタバッファ監視部１１０で監視され、その監視結果に基づいて、ジッタバッファ制御部１１１により、ジッタバッファ１０７からのパケットの読み出し速度や、受信したパケットの破棄などの処理が制御される。 A packet from the wireless communication apparatus 11 received by the packet receiving unit 106 via the communication processing unit 82 is once taken into the jitter buffer 107 and then read out. The read packet is loaded into the payload by the decoder 108. The portion is decoded and output as reproduced sound from the speaker 109. The reception status of packets in the jitter buffer 107 and the number of packets (data amount) in the jitter buffer 107 are monitored by the jitter buffer monitoring unit 110, and based on the monitoring result, the jitter buffer control unit 111 Processing such as a packet reading speed from the jitter buffer 107 and discarding of the received packet is controlled.
　図１に示した通信装置１２は、電話機能部８３に、さらに、ハンドオーバ情報取得部１１５および再生速度計算部１１６を備える。ハンドオーバ情報取得部１１５は、ＨＡ２３から転送される無線通信装置１１からのハンドオーバ情報を一定間隔毎に監視する。その結果、ハンドオーバ予定決定情報があった場合は、ハンドオーバ情報取得部１１５は、さらに、無線通信装置１１からの所要のハンドオーバ情報を取得して、その取得した所要のハンドオーバ情報を再生速度計算部１１６に供給する。 1 includes a telephone function unit 83, a handover information acquisition unit 115, and a playback speed calculation unit 116. The handover information acquisition unit 115 monitors the handover information from the wireless communication apparatus 11 transferred from the HA 23 at regular intervals. As a result, when there is handover schedule determination information, the handover information acquisition unit 115 further acquires the required handover information from the radio communication apparatus 11 and uses the acquired required handover information as the reproduction speed calculation unit 116. To supply.
　再生速度計算部１１６は、ジッタバッファ監視部１１０によるジッタバッファ１０７の監視結果と、ハンドオーバ情報取得部１１５から取得した所要のハンドオーバ情報とに基づいて、ジッタバッファ１０７のパケットの読み出し速度、すなわち受信パケットの再生速度（ここでは、ＶｏＩＰアプリケーションの再生速度）を計算し、その計算結果をジッタバッファ制御部１１１に供給する。これにより、ジッタバッファ制御部１１１は、受信パケットの再生速度が、再生速度計算部１１６で計算された再生速度となるように、ジッタバッファ１０７からの受信パケットの読み出しを制御する。 Based on the monitoring result of the jitter buffer 107 by the jitter buffer monitoring unit 110 and the required handover information acquired from the handover information acquisition unit 115, the reproduction speed calculation unit 116 reads the packet reading speed of the jitter buffer 107, that is, the received packet. The playback speed (here, the playback speed of the VoIP application) is calculated, and the calculation result is supplied to the jitter buffer control unit 111. As a result, the jitter buffer control unit 111 controls reading of the received packet from the jitter buffer 107 so that the playback speed of the received packet becomes the playback speed calculated by the playback speed calculation unit 116.
　以下、電話機能部８３の動作について説明する。図１５は、電話機能部８３の要部の動作を示すシーケンス図である。また、図１６は、無線通信装置（ＭＮ）１１、ＨＡ２３および通信装置（ＣＮ）１２間でのハンドオーバ情報の流れを示すシーケンス図である。なお、図１６において、一点鎖線は無線通信装置１１からＨＡ２３に対するハンドオーバ前のパケットの流れを示している。 Hereinafter, the operation of the telephone function unit 83 will be described. FIG. 15 is a sequence diagram showing the operation of the main part of the telephone function unit 83. FIG. 16 is a sequence diagram showing a flow of handover information between the wireless communication device (MN) 11, the HA 23 and the communication device (CN) 12. In FIG. 16, the alternate long and short dash line indicates the flow of packets before handover from the wireless communication apparatus 11 to the HA 23.
　電話機能部８３のハンドオーバ情報取得部１１５は、無線通信装置１１からのハンドオーバ情報を一定間隔毎に監視する。その結果、ハンドオーバ予定決定情報が取得された場合は、さらに、無線通信装置１１からのハンドオーバ準備時間Ts、ハンドオーバ元上り絶対遅延時間Tdup1、ハンドオーバ先上りおよび下り絶対遅延時間Tdup2およびTddn2を取得して、再生速度計算部１１６に供給する。 The handover information acquisition unit 115 of the telephone function unit 83 monitors the handover information from the wireless communication apparatus 11 at regular intervals. As a result, when the handover schedule determination information is acquired, the handover preparation time Ts, the handover source upstream absolute delay time Tdup1, the handover destination upstream and downstream absolute delay times Tdup2 and Tddn2 from the wireless communication apparatus 11 are further acquired. And supplied to the reproduction speed calculation unit 116.
　また、再生速度計算部１１６は、ジッタバッファ監視部１１０から現在のジッタバッファ１０７内の蓄積パケット数Tc(sec)を取得するとともに、ＨＡ２３までの絶対遅延時間Tdhc3を取得する。なお、ＨＡ２３までの絶対遅延時間Tdhc3は、ＨＡ２３との間でパケットを送受信してＲＴＴ（Round Trip Time）を測定し、その測定値の１／２とする。 Also, the playback speed calculation unit 116 acquires the current accumulated packet count Tc (sec) in the jitter buffer 107 from the jitter buffer monitoring unit 110, and also acquires the absolute delay time Tdhc3 to HA23. The absolute delay time Tdhc3 to the HA 23 is set to ½ of the measured value by measuring the RTT (Round Trip Time) by transmitting / receiving a packet to / from the HA 23.
　そして、再生速度計算部１１６は、これらの取得情報に基づいて、ハンドオーバ完了までの再生速度Vs (sec/sec)、すなわち、標準再生速度Vnに対する時間比を下式により算出する。 Then, the playback speed calculation unit 116 calculates the playback speed Vs (sec / sec) until the completion of the handover, that is, the time ratio with respect to the standard playback speed Vn based on the obtained information by the following formula.
［数４］
　Vs=（Tb+Tc）/(Tb+Ta)
[Equation 4]
Vs = (Tb + Tc) / (Tb + Ta)
　ここで、Tbは、ハンドオーバまでの時間 (sec)で、図１６に示すように、Tb=Ts-Tdup1-Tdhc3、から求める。また、Taは、ハンドオーバによってパケットが到着しない時間で、Ta=Tdup2+Tddn2、から求める。すなわち、ここでは、再生速度Vsとして、再生時に不所望な無音が発生せず、かつ、ハンドオーバ先からのパケットが到着する時点で、ジッタバッファ１０７内のパケットが０となる速度を算出する。 Here, Tb is the time lapse (sec) to handover, and is obtained from Tb = Ts-Tdup1-Tdhc3 as shown in FIG. Ta is the time when a packet does not arrive due to handover, and is obtained from Ta = Tdup2 + Tddn2. That is, here, as the playback speed Vs, a speed at which the packet in the jitter buffer 107 becomes 0 when no unwanted silence occurs during playback and a packet from the handover destination arrives is calculated.
　再生速度計算部１１６で算出した再生速度Vsは、ジッタバッファ制御部１１１に供給する。これにより、ジッタバッファ制御部１１１は、受信パケットを標準再生速度Vnよりも低速の算出した再生速度Vsで再生するように、ジッタバッファ４７からの受信パケットの読み出しを制御する。 The reproduction speed Vs calculated by the reproduction speed calculation unit 116 is supplied to the jitter buffer control unit 111. Thereby, the jitter buffer control unit 111 controls reading of the received packet from the jitter buffer 47 so as to reproduce the received packet at the calculated reproduction speed Vs lower than the standard reproduction speed Vn.
　その後、再生速度計算部１１６は、ハンドオーバ情報取得部１１５からハンドオーバ完了情報を取得すると、図１７に示すフローチャートに従って、ジッタバッファ制御部１１１を介してジッタバッファ１０７からの受信パケットの読み出しを制御する。 Thereafter, when the reproduction speed calculation unit 116 acquires the handover completion information from the handover information acquisition unit 115, the playback speed calculation unit 116 controls reading of the received packet from the jitter buffer 107 via the jitter buffer control unit 111 according to the flowchart shown in FIG.
　以下、図１７に示すフローチャートを参照しながら、ハンドオーバ完了後のジッタバッファ１０７の読み出し制御について説明する。先ず、再生速度計算部１１６は、ハンドオーバ完了情報を受けると、ジッタバッファ制御部１１１から、ジッタバッファ１０７内のパケット蓄積量（パケット数）およびパケット受信間隔（受信速度）を定期的に取得して（ステップＳ２１）、ジッタバッファ１０７内のパケット蓄積量が標準の蓄積量を超えるか否かを監視する（ステップＳ２２）。その結果、標準の蓄積量を超えると（Ｓ２２のYes）、再生速度制御部１１６は、過去の一定期間における受信速度の平均を算出して（ステップＳ２３）、その算出した受信速度が予め設定した再生速度Vf（１．２５）に相当する標準速度の１２５％を超えるか否かを判定する（ステップＳ２４）。 Hereinafter, the read control of the jitter buffer 107 after the completion of the handover will be described with reference to the flowchart shown in FIG. First, when receiving the handover completion information, the playback speed calculation unit 116 periodically acquires the packet accumulation amount (number of packets) and the packet reception interval (reception speed) in the jitter buffer 107 from the jitter buffer control unit 111. (Step S21), it is monitored whether or not the packet accumulation amount in the jitter buffer 107 exceeds the standard accumulation amount (Step S22). As a result, when the standard accumulation amount is exceeded (Yes in S22), the playback speed control unit 116 calculates the average reception speed in a past fixed period (step S23), and the calculated reception speed is preset. It is determined whether or not 125% of the standard speed corresponding to the reproduction speed Vf (1.25) is exceeded (step S24).
　ここで、受信速度が１２５％を超えていれば（Ｓ２４のYes）、再生速度計算部１１６は、ジッタバッファ制御部１１１に対して再生速度Vfで高速再生を開始するように指示して（ステップＳ２５）、ジッタバッファ１０７内のパケット蓄積量が標準になったか否かを監視する（ステップＳ２６）。 Here, if the reception speed exceeds 125% (Yes in S24), the reproduction speed calculation unit 116 instructs the jitter buffer control unit 111 to start high-speed reproduction at the reproduction speed Vf (Step S24). S25), it is monitored whether or not the packet accumulation amount in the jitter buffer 107 becomes standard (step S26).
　これに対し、ステップＳ２４において、受信速度が１２５％を超えていなければ（Ｓ２４のNo）、再生速度計算部１１６は、次に、受信速度が標準速度（１００％）か否かを判定する（ステップＳ２７）。その結果、標準速度を超えていれば（Ｓ２７のYes）、再生速度計算部１１６は、ジッタバッファ制御部１１１に対して、ステップＳ２３で計算した受信速度と同じ速度で高速再生を開始するように指示して（ステップＳ２８）、ステップＳ２６に移行する。 On the other hand, if the reception speed does not exceed 125% in step S24 (No in S24), the reproduction speed calculation unit 116 next determines whether or not the reception speed is the standard speed (100%) ( Step S27). As a result, if the standard speed is exceeded (Yes in S27), the playback speed calculation unit 116 starts high-speed playback at the same speed as the reception speed calculated in step S23 with respect to the jitter buffer control unit 111. Instructed (step S28), the process proceeds to step S26.
　再生速度計算部１１６は、その後も、ジッタバッファ１０７の蓄積量およびパケット受信間隔（受信速度）を定期的に監視し続ける。そして、ステップＳ２６において、ジッタバッファ１０７内のパケット蓄積量が標準になると（Ｓ２６のYes）、パケット受信間隔（受信速度）の平均が、標準値から一定範囲内か否かを判定する（ステップＳ２９）。その結果、パケット蓄積量が標準で、かつパケット受信間隔が一定範囲内（Ｓ２９のYes）になると、ジッタバッファ１０７を通常の制御に戻すようにジッタバッファ制御部１１１に指示して（ステップＳ３０）、ハンドオーバ時の制御を終了する。なお、ステップＳ２３において算出した受信速度の平均が、ステップＳ２７において、標準速度を超えていない場合は（Ｓ２７のNo）、ステップＳ３０に移行して、同様に、ジッタバッファ１０７を通常の制御に戻す。 The reproduction speed calculation unit 116 continues to regularly monitor the accumulation amount of the jitter buffer 107 and the packet reception interval (reception speed) thereafter. In step S26, when the packet accumulation amount in the jitter buffer 107 becomes standard (Yes in S26), it is determined whether or not the average packet reception interval (reception speed) is within a certain range from the standard value (step S29). ). As a result, when the packet accumulation amount is standard and the packet reception interval is within a certain range (Yes in S29), the jitter buffer control unit 111 is instructed to return the jitter buffer 107 to normal control (step S30). Then, the control at the time of handover is terminated. If the average reception speed calculated in step S23 does not exceed the standard speed in step S27 (No in S27), the process proceeds to step S30 and similarly returns the jitter buffer 107 to normal control. .
　図１８は、上述した通信装置１２によるパケットの再生制御を説明するための図である。図１８（ａ）は、ジッタバッファ１０７が単位時間に受信するパケット数、図１８（ｂ）は、ジッタバッファ１０７内のパケット蓄積量、図１８（ｃ）は、再生速度をそれぞれ示す。ここでは、図１８（ａ）に示すように、第２無線通信ネットワーク１６にハンドオーバされた最初の部分では、ジッタバッファ１０７は、標準受信パケット数の１２５％より多いパケット数を受信し、その後は、標準受信パケット数と等しいパケット数を受信した場合を例示している。なお、図１８（ｂ）において、パケット蓄積量Tnは、標準再生速度Vnに相当する標準蓄積量を示す。 FIG. 18 is a diagram for explaining packet reproduction control by the communication device 12 described above. 18A shows the number of packets received by the jitter buffer 107 per unit time, FIG. 18B shows the amount of packets stored in the jitter buffer 107, and FIG. 18C shows the playback speed. Here, as shown in FIG. 18 (a), in the first part handed over to the second wireless communication network 16, the jitter buffer 107 receives the number of packets larger than 125% of the standard number of received packets, and thereafter In this example, the number of packets equal to the standard number of received packets is received. In FIG. 18B, the packet accumulation amount Tn indicates a standard accumulation amount corresponding to the standard reproduction speed Vn.
　図１８から明らかなように、通信装置１２は、ハンドオーバ予定通知を含むハンドオーバ情報に基づいて、アプリケーションの再生速度を、標準再生速度Vnから、ハンドオーバ先からのパケットの受信開始時点でジッタバッファ１０７内のパケット数が０となる定速度の再生速度Vsに低下させる。その後、ハンドオーバが完了して、ジッタバッファ１０７内のパケット蓄積量およびパケットの受信間隔が標準に戻ったのを確認して、標準再生速度Vnに戻すようにしている。 As is apparent from FIG. 18, the communication device 12 determines the application reproduction speed from the standard reproduction speed Vn based on the handover information including the handover schedule notification, in the jitter buffer 107 at the reception start time of the packet from the handover destination. Is reduced to a constant reproduction speed Vs at which the number of packets becomes zero. After that, it is confirmed that the handover is completed and the packet accumulation amount and the packet reception interval in the jitter buffer 107 have returned to the standard, and the standard reproduction speed Vn is restored.
　したがって、ハンドオーバによってパケットが到着しない期間（Ta=Tdup2+Tddn2）でも、より標準再生速度に近い定速度の再生速度でアプリケーションを再生することができるので、再生品質およびリアルタイム性を低下させることがなくなる。 Therefore, even during a period when packets do not arrive due to handover (Ta = Tdup2 + Tddn2), the application can be played back at a constant playback speed that is closer to the standard playback speed, so that the playback quality and real-time performance are not degraded. .
　なお、ジッタバッファ制御部１１１による、標準再生速度Vnよりも低速の再生速度Vsによるパケットの再生速度制御は、例えば、以下に説明する第１の再生速度制御方法または第２の再生速度制御方法のいずれかにより実行する。 Note that the packet playback speed control at the playback speed Vs lower than the standard playback speed Vn by the jitter buffer controller 111 is, for example, the first playback speed control method or the second playback speed control method described below. Execute by either.
（ａ）第１の再生速度制御方法
　標準再生速度Vnに対するジッタバッファ１０７からのパケットの読み出し間隔をTR1、（Tb+Tc）/(Tb+Ta)をk、算出した再生速度Vsに対応するジッタバッファ１０７からのパケットの読み出し間隔をTR、とするとき、TR=TR1/k、とする。例えば、標準再生速度Vnでは、ジッタバッファ１０７内のパケットを２０msecの間隔で読み出して再生するＶｏＩＰアプリケーションにおいて、再生速度Vsを標準再生速度Vnの８０％（k=0.8）とする場合には、ジッタバッファ４７からのパケットの読み出し間隔TRを、TR=20/0.8(msec)、とする。 (A) First playback speed control method TR1 is the packet reading interval from the jitter buffer 107 with respect to the standard playback speed Vn, (Tb + Tc) / (Tb + Ta) is k, and the jitter corresponding to the calculated playback speed Vs. When the interval for reading packets from the buffer 107 is TR, TR = TR1 / k. For example, at the standard playback speed Vn, in a VoIP application that reads and plays back packets in the jitter buffer 107 at intervals of 20 msec, when the playback speed Vs is 80% (k = 0.8) of the standard playback speed Vn, jitter The packet reading interval TR from the buffer 47 is TR = 20 / 0.8 (msec).
（ｂ）第２の再生速度制御方法
　ハンドオーバのための再生速度のコントロールを開始すると、その直後に再生したパケットのタイムスタンプと、その再生時間とを組み合わせて記録する。その後のパケットについては、下式で示す時間Tvに、ジッタバッファ１０７から読み出して再生する。なお、下式において、TDは、遅延時間で、初期値は０である。
［数５］
　Tv=（パケットのタイムスタンプ－最初のパケットのタイムスタンプ）＋（最初のパケットの再生時間＋TD）
(B) Second Playback Speed Control Method When playback speed control for handover is started, the time stamp of the packet played back immediately after that is recorded in combination with the playback time. Subsequent packets are read from the jitter buffer 107 and reproduced at time Tv shown in the following equation. In the following equation, TD is a delay time, and the initial value is 0.
[Equation 5]
Tv = (packet time stamp-first packet time stamp) + (first packet playback time + TD)
　ここで、ジッタバッファ１０７からパケットを読み出す際、[{Vn/(Vn-Vs)}-1]個目に読み出したパケットは、コピーしてデコーダ１０８内のメモリに記憶し、コピー元のパケットを再生した後、次の再生タイミングでコピーしたパケットを読み出して再生する。例えば、再生速度Vsを、標準再生速度Vnの８０％とする場合には、図１９に示すように、ジッタバッファ１０７内の順次の４個のパケットＰ１～Ｐ４を順番に読み出して再生するとともに、４個目のパケットＰ４はコピーし、そのコピーしたパケットＰ４′は、コピー元のパケットＰ４を再生した後、次の再生タイミングで再生する。その後、ジッタバッファ１０７からパケットＰ５を読み出す際は、上記のTDを、コピーによる再生間隔の時間分増加する。なお、[{Vn/(Vn-Vs)}-1]個目に読み出すパケットが、届いていなかったり、破棄されたりして、ジッタバッファ１０７にない場合には、次の再生タイミングのパケットに対して、同様の処理を行う。 Here, when reading a packet from the jitter buffer 107, the [{Vn / (Vn-Vs)}-1] -th read packet is copied and stored in the memory in the decoder 108, and the copy source packet is stored. After reproduction, the copied packet is read and reproduced at the next reproduction timing. For example, when the playback speed Vs is set to 80% of the standard playback speed Vn, as shown in FIG. 19, the sequential four packets P1 to P4 in the jitter buffer 107 are sequentially read and played back, The fourth packet P4 is copied, and the copied packet P4 ′ is reproduced at the next reproduction timing after reproducing the copy source packet P4. Thereafter, when reading the packet P5 from the jitter buffer 107, the TD is increased by the reproduction interval time by copying. If the [{Vn / (Vn−Vs)} − 1] -th packet to be read has not arrived or has been discarded and is not in the jitter buffer 107, the packet at the next reproduction timing is The same processing is performed.
　以上の処理により、通信装置１２は、無線通信装置１１のハンドオーバ時にパケットの到着しない期間が発生し、その後、無線通信装置１１から、蓄積されたパケットが高速に到着するという状態に適切に対応して、最適な速度でパケットを再生することができる。 Through the above processing, the communication device 12 appropriately responds to a state in which a period in which packets do not arrive occurs at the time of handover of the wireless communication device 11, and then the accumulated packets arrive from the wireless communication device 11 at high speed. Thus, packets can be played back at an optimum speed.
　なお、上記第１実施の形態では、モバイルＩＰのリバーストンネリングまたはＮＥＭＯを使用して、無線通信装置１１からＨＡ２３を経由して通信装置１２にパケットを送信する場合を例示したが、ハンドオーバによる無線通信装置１１から通信装置１２への送信パケットのロストは、モバイルＩＰｖ６で経路の最適化を行い、無線通信装置１１と通信装置１２との間で直接パケットの送受信を行う場合にも、ハンドオーバによる経路の遅延時間の差により同様に生じる。したがって、このような場合にも、上記実施の形態と同様にして、ハンドオーバ時に無線通信装置１１で送信するパケットを蓄積して、ハンドオーバ後に蓄積したパケットを送信することにより、パケットロスを防ぐことができる。 In the first embodiment, the case where a packet is transmitted from the wireless communication apparatus 11 to the communication apparatus 12 via the HA 23 using mobile IP reverse tunneling or NEMO is exemplified. Lost of the transmission packet from the device 11 to the communication device 12 optimizes the route with Mobile IPv6, and also when the packet is directly transmitted and received between the wireless communication device 11 and the communication device 12, This also occurs due to the difference in delay time. Accordingly, even in such a case, the packet loss can be prevented by accumulating the packets transmitted by the wireless communication apparatus 11 at the time of handover and transmitting the accumulated packets after the handover in the same manner as in the above embodiment. it can.
　また、上記実施の形態では、第１無線通信ネットワーク１５よりも上りの絶対遅延時間が短い第２無線通信ネットワーク１６へハンドオーバする場合について説明したが、逆に、第２無線通信ネットワーク１６から上りの絶対遅延時間が長い第１無線通信ネットワーク１５へハンドオーバする場合にも、同様にしてパケットロスを防ぐことができる。この場合は、無線通信装置（ＭＮ）１１がBinding Update等のハンドオーバ要求情報を送信した時点から、Tsttlow=Tdup1-Tdup2、先の時点を始点として、この始点から、無線通信装置（ＭＮ）１１がＨＡ２３からBinding Ack等のハンドオーバ完了情報を受信する時点までに、ハンドオーバ元から送信されたパケットがロストすることになる。したがって、この場合のロスト期間Tlostは、Tlost=Tdup1+Tddn2、となるので、この期間の送信パケットは送信バッファ５７に蓄積して、ハンドオーバ完了後に高速送信すればよい。なお、この場合、ハンドオーバによって、ＨＡ２３が無線通信装置１１からパケットを受信しない期間は、Tdup2+Tddn2、となる。 In the above embodiment, a case has been described in which a handover is made to the second wireless communication network 16 whose uplink absolute delay time is shorter than that of the first wireless communication network 15. Similarly, when handing over to the first wireless communication network 15 having a long absolute delay time, packet loss can be prevented. In this case, Tsttlow = Tdup1-Tdup2 from the time when the wireless communication device (MN) 11 transmits handover request information such as Binding Update, and the wireless communication device (MN) 11 starts from this starting point. By the time when handover completion information such as Binding 時点 Ack is received from the HA 23, the packet transmitted from the handover source is lost. Therefore, since the lost period Tlost in this case is Tlost = Tdup1 + Tddn2, the transmission packets in this period may be stored in the transmission buffer 57 and transmitted at high speed after the handover is completed. In this case, the period during which the HA 23 does not receive a packet from the wireless communication apparatus 11 due to handover is Tdup2 + Tddn2.
　さらに、上述した通信装置１２においては、再生速度計算部１１６で再生速度Vsを計算する際、ハンドオーバ先からのパケットの受信開始時点で、ジッタバッファ１０７内のパケット数が０となるようにしたが、ハンドオーバ先からのパケットの受信開始時点で、ジッタバッファ１０７内のパケット数が所定数となるように、再生速度Vsを計算することもできる。 Further, in the communication apparatus 12 described above, when the reproduction speed calculation unit 116 calculates the reproduction speed Vs, the number of packets in the jitter buffer 107 is zero at the start of packet reception from the handover destination. The playback speed Vs can also be calculated so that the number of packets in the jitter buffer 107 becomes a predetermined number at the start of reception of packets from the handover destination.
（第２実施の形態）
　次に、本発明の第２実施の形態に係る通信装置ついて説明する。 (Second Embodiment)
Next, a communication apparatus according to the second embodiment of the present invention will be described.
　図２０は、本発明の第２実施の形態に係る通信装置が使用可能な通信ネットワークの概略構成を示す図である。図２０に示す通信ネットワークは、図１と同様の構成を有している。移動ノードである無線通信装置（ＭＮ）１２１は、第１無線通信ネットワーク１５と第２無線通信ネットワーク１６との間で、ハンドオーバが可能となっており、対向ノードである通信装置（ＣＮ）１２２との間で、リアルタイム通信系のアプリケーションであるＶｏＩＰによる通話を行うものと仮定する。なお、図２０に示した通信ネットワークにおいて、図１に示した通信ネットワークと同様の作用を成す構成要素には、同一の参照符号を付して説明を省略する。 FIG. 20 is a diagram showing a schematic configuration of a communication network that can be used by the communication apparatus according to the second embodiment of the present invention. The communication network shown in FIG. 20 has the same configuration as that in FIG. The wireless communication device (MN) 121 that is a mobile node can be handed over between the first wireless communication network 15 and the second wireless communication network 16, and the communication device (CN) 122 that is the opposite node , VoIP, which is a real-time communication system application, is assumed to make a call. In the communication network shown in FIG. 20, the same reference numerals are assigned to the same components as those in the communication network shown in FIG.
　通信装置１２２は、例えば送受話器１２２ａが接続され、電話機能部としてのソフトフォンがインストールされたパーソナルコンピュータからなり、図示しないインターネットサービスプロバイダを介して通信ネットワークであるインターネット１８に接続されている。 The communication device 122 is composed of, for example, a personal computer to which a handset 122a is connected and a soft phone as a telephone function unit is installed, and is connected to the Internet 18 as a communication network through an Internet service provider (not shown).
　図２０において、無線通信装置１２１は、ＨＡ２３に第１無線通信ネットワーク１５のＩＰアドレスを気付けアドレス（第１無線ＣｏＡ）として登録して、第１無線通信ネットワーク１５を介して通信装置１２２と通信を行っている状態から、第２無線通信ネットワーク１６へハンドオーバするものとする。 20, the wireless communication device 121 registers the IP address of the first wireless communication network 15 in the HA 23 as a care-of address (first wireless CoA), and communicates with the communication device 122 via the first wireless communication network 15. It is assumed that handover is performed from the current state to the second wireless communication network 16.
　図２１は、図２０に示した無線通信装置１２１の概略構成を示す機能ブロック図である。無線通信装置１２１は、図２に示した無線通信装置１１と同様に、第１無線通信ネットワーク１５に対応する第１無線Ｉ／Ｆ（インターフェース）１３１と、第２無線通信ネットワーク１６に対応する第２無線Ｉ／Ｆ１３２と、ＶｏＩＰのアプリケーションを実行する電話機能部１３３と、第１無線通信ネットワーク１５および第２無線通信ネットワーク１６への接続を制御する通信処理部１３４と、第１無線通信ネットワーク１５および第２無線通信ネットワーク１６の無線情報を取得する無線情報取得部１３５と、第１無線通信ネットワーク１５と第２無線通信ネットワーク１６との間のハンドオーバを制御するハンドオーバ制御部１３６と、を有する。 FIG. 21 is a functional block diagram showing a schematic configuration of the wireless communication apparatus 121 shown in FIG. Similarly to the wireless communication device 11 illustrated in FIG. 2, the wireless communication device 121 includes a first wireless I / F (interface) 131 corresponding to the first wireless communication network 15 and a second wireless communication network 16 corresponding to the second wireless communication network 16. Two wireless I / Fs 132, a telephone function unit 133 that executes a VoIP application, a communication processing unit 134 that controls connection to the first wireless communication network 15 and the second wireless communication network 16, and a first wireless communication network 15 And a wireless information acquisition unit 135 that acquires wireless information of the second wireless communication network 16, and a handover control unit 136 that controls a handover between the first wireless communication network 15 and the second wireless communication network 16.
　通信処理部１３４は、図２に示した通信処理部３４と同様に、電話機能部１３３と通信装置１２２との間で、第１無線通信ネットワーク１５または第２無線通信ネットワーク１６を介して通話を行うとともに、ハンドオーバ制御部１３６による制御のもとに、ＨＡ２３と通信するように、第１無線Ｉ／Ｆ１３１または第２無線Ｉ／Ｆ１３２の接続を制御する。 Similar to the communication processing unit 34 shown in FIG. 2, the communication processing unit 134 makes a call between the telephone function unit 133 and the communication device 122 via the first wireless communication network 15 or the second wireless communication network 16. In addition, the connection of the first wireless I / F 131 or the second wireless I / F 132 is controlled so as to communicate with the HA 23 under the control of the handover control unit 136.
　無線情報取得部１３５は、図２に示した無線情報取得部３５と同様に、無線情報として、第１無線Ｉ／Ｆ１３１および第２無線Ｉ／Ｆ１３２から、それぞれ対応する第１無線通信ネットワーク１５および第２無線通信ネットワーク１６の通信品質（例えば、ＲＳＳＩ）を取得し、その取得した通信品質をハンドオーバ制御部１３６に供給する。 Similarly to the wireless information acquisition unit 35 illustrated in FIG. 2, the wireless information acquisition unit 135 receives the first wireless communication network 15 and the corresponding wireless information from the first wireless I / F 131 and the second wireless I / F 132 as wireless information. The communication quality (for example, RSSI) of the second wireless communication network 16 is acquired, and the acquired communication quality is supplied to the handover control unit 136.
　ハンドオーバ制御部１３６は、無線情報取得部１３５からの通信品質に基づいて、ハンドオーバを予定するか否か、すなわちハンドオーバの準備を開始するか否かの決定を含むハンドオーバ情報を生成し、そのハンドオーバ情報に基づいてハンドオーバを制御する。 Based on the communication quality from the radio information acquisition unit 135, the handover control unit 136 generates handover information including a decision whether to schedule a handover, that is, whether to start preparation for handover, and the handover information Based on the above, handover is controlled.
　以下、ハンドオーバ制御部１３６の動作について、さらに詳細に説明する。 Hereinafter, the operation of the handover control unit 136 will be described in more detail.
　ハンドオーバ制御部１３６は、例えば、図２に示したハンドオーバ制御部３６と同様にして、第１無線Ｉ／Ｆ１３１および第２無線Ｉ／Ｆ１３２から無線情報取得部１３５を経由してそれぞれ取得した通信品質に基づいて、ハンドオーバの予定を決定する。 The handover control unit 136, for example, in the same way as the handover control unit 36 shown in FIG. 2, the communication quality acquired from the first wireless I / F 131 and the second wireless I / F 132 via the wireless information acquisition unit 135, respectively. Based on the above, the handover schedule is determined.
　ハンドオーバ制御部１３６は、ハンドオーバ予定を決定すると、ハンドオーバ開始までの時間、すなわちハンドオーバ要求情報であるRegistration Request（ＮＥＭＯでは、Binding Update）を送信するまでの時間であるハンドオーバ準備時間Ts(sec)と、現在使用中の無線通信ネットワーク（ここでは、第１無線通信ネットワーク１５）における無線通信装置１１とＨＡ２３との間の上りの絶対遅延時間Tdup1(sec)および下りの絶対遅延時間Tddn1(sec)と、ハンドオーバ先の無線通信ネットワーク（ここでは、第２無線通信ネットワーク１６）における無線通信装置１２１とＨＡ２３との間の上りおよび下りの絶対遅延時間Tdup2(sec)およびTddn2(sec)と、ＨＡ２３のハンドオーバ完了時すなわちハンドオーバ要求情報がＨＡ２３に到着した時点のハンドオーバ先の無線通信ネットワークにおける下りの予測帯域Rbdn2(bps) とを取得する。 When the handover control unit 136 determines the handover schedule, the handover preparation time Ts (sec), which is the time until the start of the handover, that is, the time until the RegistrationRegRequest (Binding Update in NEMO) is transmitted, An uplink absolute delay time Tdup1 (sec) and a downlink absolute delay time Tddn1 (sec) between the wireless communication device 11 and the HA 23 in the currently used wireless communication network (here, the first wireless communication network 15); Up and down absolute delay times Tdup2 (sec) and Tddn2 (sec) between the radio communication apparatus 121 and the HA 23 in the handover destination radio communication network (here, the second radio communication network 16), and the handover of the HA 23 is completed. The handover destination information when the handover request information arrives at the HA 23 And acquires the calculated bandwidth Rbdn2 (bps) of the downlink on line communication network.
　そして、ハンドオーバ制御部１３６は、これらの取得情報を、所要のハンドオーバ情報として、ハンドオーバの予定決定を示すハンドオーバ予定決定情報を含めて、電話機能部１３３に供給する。また、電話機能部１３３は、ハンドオーバ制御部１３６から取得したハンドオーバ情報を、後述する絶対遅延時間の比較結果に応じて、ハンドオーバ予告メッセージとして、ＨＡ２３を介して通信装置１２に選択的に送信する。 Then, the handover control unit 136 supplies the acquired information as necessary handover information to the telephone function unit 133 including handover schedule determination information indicating schedule determination of handover. In addition, the telephone function unit 133 selectively transmits the handover information acquired from the handover control unit 136 to the communication device 12 via the HA 23 as a handover advance notice message according to the comparison result of absolute delay time described later.
　ここで、ハンドオーバ制御部３６による、上記のハンドオーバ準備時間Ts、ハンドオーバ元上りおよび下り絶対遅延時間Tdup1およびTddn1、ハンドオーバ先上りおよび下り絶対遅延時間Tdup2およびTddn2、並びに、ハンドオーバ先予測帯域Rbdn2は、例えば、第１実施の形態において説明した取得方法によりそれぞれ取得する。 Here, the handover preparation time Ts, handover source uplink and downlink absolute delay times Tdup1 and Tddn1, handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, and handover destination predicted bandwidth Rbdn2 by the handover control unit 36 are, for example, Each is acquired by the acquisition method described in the first embodiment.
　すなわち、ハンドオーバ準備時間Tsは、図４（ａ）および（ｂ）を用いて説明した取得方法により取得する。また、絶対遅延時間Tdup1、Tddn1、Tdup2、Tddn2は、第１～第３の絶対遅延時間取得方法のいずれかによって取得して、無線通信ネットワーク毎に、ハンドオーバ制御部１３６内のメモリ（図示せず）に記憶しておく。 That is, the handover preparation time Ts is acquired by the acquisition method described with reference to FIGS. 4 (a) and 4 (b). The absolute delay times Tdup1, Tddn1, Tdup2, and Tddn2 are acquired by any one of the first to third absolute delay time acquisition methods, and are stored in a memory (not shown) in the handover control unit 136 for each radio communication network. ).
　例えば、第１の絶対遅延時間取得方法による場合は、第１無線Ｉ／Ｆ１３１および第２無線Ｉ／Ｆ１３２を介してそれぞれ受信したＨＡ２３からの計測用パケットの受信時刻と、当該計測用パケットのタイムスタンプとから、対応するネットワークの絶対遅延時間Tdup1、Tddn1、Tdup2、Tddn2を計測する。 For example, in the case of the first absolute delay time acquisition method, the reception time of the measurement packet from the HA 23 received via the first wireless I / F 131 and the second wireless I / F 132, and the time of the measurement packet From the stamp, the absolute delay times Tdup1, Tddn1, Tdup2, and Tddn2 of the corresponding network are measured.
　また、第２の絶対遅延時間取得方法による場合は、ＨＡ２３に対して、第１無線通信ネットワーク１５および第２無線通信ネットワーク１６の双方から、ＰＩＮＧやＲＴＣＰ等の計測用パケットの送信時刻と、その返信の受信時刻とに基づいて、対応するネットワークの絶対遅延時間Tdup1、Tddn1、Tdup2、Tddn2を計測する。 Further, in the case of the second absolute delay time acquisition method, the transmission time of measurement packets such as PING and RTCP from both the first wireless communication network 15 and the second wireless communication network 16 to the HA 23 and its Based on the reception time of the reply, the absolute delay times Tdup1, Tddn1, Tdup2, and Tddn2 of the corresponding network are measured.
　また、第３の絶対遅延時間取得方法による場合は、絶対遅延時間Tdup1、Tdup2、Tddn2については、上記の［数２］および［数３］により取得し、絶対遅延時間Tddn1については、下式により取得する。 In the case of the third absolute delay time acquisition method, the absolute delay times Tdup1, Tdup2, and Tddn2 are acquired by the above [Equation 2] and [Equation 3], and the absolute delay time Tddn1 is obtained by the following equation. get.
［数６］
　Tddn1=Tn3+Trdn3=Tn1+Trdn1+(Tn3-Tn1)
[Equation 6]
Tddn1 = Tn3 + Trdn3 = Tn1 + Trdn1 + (Tn3-Tn1)
　また、ハンドオーバ先の下りの予測帯域Rbdn2は、ＨＡ２３のハンドオーバ完了時におけるハンドオーバ先の無線通信ネットワークにおける下りの無線状態を予測して取得する。このため、ハンドオーバ制御部１３６には、例えば、図６に示したような無線状態（通信品質）とスループット（予測帯域）との変換テーブルを予め記憶しておく。ハンドオーバ制御部３６は、例えば、ハンドオーバ予定決定時点におけるハンドオーバ先の無線状況と、その時点から所定時間前のハンドオーバ先の無線状況とに基づいて、ハンドオーバ完了時のハンドオーバ先の無線状態を線形に予測し、その予測した無線状態に基づいて、図６の変換テーブルから、ハンドオーバ完了時点のハンドオーバ先予測帯域Rbdn2を取得する。ここで、ハンドオーバ完了時点は、ハンドオーバ予定決定時点から、ハンドオーバ準備時間Tsと、ハンドオーバ先の無線通信ネットワーク（ここでは、第２無線通信ネットワーク１６）におけるＨＡ２３と無線通信装置１１との間の上りの絶対遅延時間Trup2とを加算した時点とする。 Also, the downlink predicted bandwidth Rbdn2 of the handover destination is obtained by predicting the downlink radio state in the handover destination radio communication network when the handover of the HA 23 is completed. For this reason, the handover control unit 136 stores, for example, a conversion table between the radio state (communication quality) and the throughput (predicted bandwidth) as shown in FIG. For example, the handover control unit 36 linearly predicts the handover destination radio status at the completion of the handover based on the handover destination radio status at the time when the handover schedule is determined and the handover destination radio status a predetermined time before that time. Then, based on the predicted radio state, the handover destination predicted bandwidth Rbdn2 at the time of handover completion is acquired from the conversion table of FIG. Here, the handover completion time is determined from the handover schedule determination time to the handover preparation time Ts and the uplink between the HA 23 and the radio communication device 11 in the handover destination radio communication network (here, the second radio communication network 16). The absolute delay time Trup2 is added.
　以上のようにして、ハンドオーバ制御部１３６は、ハンドオーバ準備時間Ts、ハンドオーバ元上りおよび下り絶対遅延時間Tdup1およびTddn1、ハンドオーバ先上りおよび下り絶対遅延時間Tdup2およびTddn2、並びに、ハンドオーバ先下り予測帯域Rbdn2を取得すると、それらの取得情報を、ハンドオーバの予定決定を示すハンドオーバ予定決定情報とともに、所要のハンドオーバ情報として、電話機能部１３３に供給する。 As described above, the handover control unit 136 sets the handover preparation time Ts, the handover source uplink and downlink absolute delay times Tdup1 and Tddn1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, and the handover destination downlink predicted bandwidth Rbdn2. Upon acquisition, the acquired information is supplied to the telephone function unit 133 as required handover information together with handover schedule determination information indicating handover schedule determination.
　また、ハンドオーバ制御部１３６は、ハンドオーバ予定を決定した場合は、ハンドオーバ処理を実行する。 In addition, when the handover control unit 136 determines a handover schedule, the handover control unit 136 executes a handover process.
　図２２は、無線通信装置１２１とＨＡ２３との間のハンドオーバ処理を説明するためのシーケンス図である。図２２に示すように、無線通信装置（ＭＮ）１２１のハンドオーバ制御部１３６は、ハンドオーバ予定を決定すると、通信処理部１３４を制御して、第２無線Ｉ／Ｆ１３２を第２無線通信ネットワーク１６に接続する。その後、ハンドオーバ制御部１３６は、ハンドオーバ準備時間Tsが経過した時点で、ハンドオーバ先の第２無線通信ネットワーク１６を介してＨＡ２３にハンドオーバ要求情報であるRegistration Request（ＮＥＭＯでは、Binding Update）を送信する。 FIG. 22 is a sequence diagram for explaining a handover process between the wireless communication apparatus 121 and the HA 23. As illustrated in FIG. 22, when the handover control unit 136 of the wireless communication apparatus (MN) 121 determines a handover schedule, the handover control unit 136 controls the communication processing unit 134 to transfer the second wireless I / F 132 to the second wireless communication network 16. Connecting. Thereafter, when the handover preparation time Ts elapses, the handover control unit 136 transmits a Registration request (handling update in NEMO) to the HA 23 via the second wireless communication network 16 that is the handover destination.
　ＨＡ２３は、ハンドオーバ要求情報を受信すると、ハンドオーバ先のＩＰアドレスを気付けアドレス（第２無線ＣｏＡ）として登録して、ハンドオーバ完了情報であるRegistration Reply（ＮＥＭＯでは、Binding Acknowledge）を、第２無線通信ネットワーク１６を介して無線通信装置１２１に返信する。なお、ＨＡ２３は、無線通信装置１２１に対して一つの気付けアドレスのみを登録する。したがって、ハンドオーバ先の気付けアドレス（第２無線ＣｏＡ）は、既に登録されているハンドオーバ元の気付けアドレス（第１無線ＣｏＡ）に上書きして登録する。 Upon receipt of the handover request information, the HA 23 registers the IP address of the handover destination as a care-of address (second wireless CoA), and registers Registration Reply (Binding Acknowledge in NEMO) as the second wireless communication network. 16 to the wireless communication apparatus 121 via Note that the HA 23 registers only one care-of address with the wireless communication apparatus 121. Therefore, the care-of address of the handover destination (second radio CoA) is registered by overwriting the care-of address of the handover source (first radio CoA) already registered.
　その後、ハンドオーバ制御部１３６は、ＨＡ２３から返信されるハンドオーバ完了情報であるRegistration Reply（ＮＥＭＯでは、Binding Acknowledge）を受信すると、ハンドオーバ先の第２無線通信ネットワーク１６によりパケットの送受信を開始するとともに、通信処理部１３４を制御して、第１無線Ｉ／Ｆ３１とハンドオーバ元の第１無線通信ネットワーク１５との接続を切断する。なお、ハンドオーバ制御部１３６は、ＨＡ２３からハンドオーバ完了情報を受信すると、その旨を示すハンドオーバ完了通知を、ハンドオーバ情報として電話機能部１３３に送信する。 Thereafter, upon receiving Registration ハ ン ド オ ー バ Reply (Binding Acknowledge in NEMO) as handover completion information returned from the HA 23, the handover control unit 136 starts transmission / reception of a packet by the second wireless communication network 16 at the handover destination and performs communication. The processing unit 134 is controlled to disconnect the connection between the first wireless I / F 31 and the first wireless communication network 15 that is the handover source. When the handover control unit 136 receives the handover completion information from the HA 23, the handover control unit 136 transmits a handover completion notification indicating that to the telephone function unit 133 as the handover information.
　図２２から明らかなように、ハンドオーバ元の第１無線通信ネットワーク１５を経由する下りの絶対遅延時間Tddn1が、ハンドオーバ先の第２無線通信ネットワーク１６を経由する下りの絶対遅延時間Tddn2よりも長いと、無線通信装置（ＭＮ）１２１には、ハンドオーバ元の第１無線Ｉ／Ｆ１３１を第１無線通信ネットワーク１５から切断した後、ＨＡ２３からハンドオーバ元の第１無線通信ネットワーク１５に転送されたパケットが受信できなくなって、パケットのロストが生じることになる。 As is apparent from FIG. 22, if the downlink absolute delay time Tddn1 passing through the first wireless communication network 15 as the handover source is longer than the absolute delay time Tddn2 passing through the second wireless communication network 16 as the handover destination. The wireless communication device (MN) 121 receives the packet transferred from the HA 23 to the first wireless communication network 15 of the handover source after disconnecting the first wireless I / F 131 of the handover source from the first wireless communication network 15. It becomes impossible and the lost packet occurs.
　図２３は、この場合のパケットロスの発生を説明するための図である。ここでは、便宜上、ＮＥＭＯを例にとって説明する。図２３に示すように、無線通信装置（ＭＮ）１２１は、ＨＡ２３からBinding Ackを受信すると、その後は、ハンドオーバ先からのパケットのみを受信することになる。このため、ハンドオーバ元の下りの絶対遅延時間Tddn1が、ハンドオーバ先の下りの絶対遅延時間Tddn2よりも長い場合は、無線通信装置（ＭＮ）１２１がBinding Ackを受信した時点から、（Tddn1-Tddn2）先の期間における、ハンドオーバ元の第１無線通信ネットワーク１５から送信されたパケットが無線通信装置（ＭＮ）１２１で受信できず、この期間（Tddn1-Tddn2）がパケットのロスト期間Tlostとなる。 FIG. 23 is a diagram for explaining the occurrence of packet loss in this case. Here, for convenience, NEMO will be described as an example. As illustrated in FIG. 23, when the wireless communication device (MN) 121 receives Binding Ack from the HA 23, thereafter, only the packet from the handover destination is received. For this reason, when the absolute delay time Tddn1 of the handover source downlink is longer than the absolute delay time Tddn2 of the handover destination downlink, (Tddn1-Tddn2) from the time when the wireless communication device (MN) 121 receives BindingckAck. The packet transmitted from the first wireless communication network 15 that is the handover source in the previous period cannot be received by the wireless communication apparatus (MN) 121, and this period (Tddn1-Tddn2) becomes the lost period Tlost of the packet.
　ここで、通信装置（ＣＮ）１２２が、ロスト期間Tlostに最初に送信するデータDat(n1)の送信タイミングをT1、最後に送信するデータDat(n2)の送信タイミングをT2とすると、通信装置（ＣＮ）１２２が、ＨＡ２３を経て無線通信装置（ＭＮ）１２１からのハンドオーバ予告メッセージMsg(HO)を受信した時点から、データDat(n1)の送信タイミングT1までの期間Tlowstt(sec)は、ハンドオーバ予告メッセージMsg(HO)に含まれるハンドオーバ情報と、通信装置（ＣＮ）１２２とＨＡ２３との間の絶対遅延時間Tdnとを用いて、以下のように求めることができる。なお、ＨＡ２３との間の絶対遅延時間Tdnは、ＨＡ２３との間でパケットを送受信してＲＴＴ（Round Trip Time）を測定し、その測定値を１／２することにより求めることができる。 Here, the communication device (CN) 122 assumes that the transmission timing of the data Dat (n1) transmitted first in the lost period Tlost is T1, and the transmission timing of the data Dat (n2) transmitted last is T2. CN) 122 receives a handover notice message Msg (HO) from the wireless communication apparatus (MN) 121 via HA 23, and until a transmission timing T1 of data Dat (n1), Tlowstt (sec) is a handover notice. Using the handover information included in the message Msg (HO) and the absolute delay time Tdn between the communication device (CN) 122 and the HA 23, it can be obtained as follows. The absolute delay time Tdn with the HA 23 can be obtained by transmitting / receiving a packet to / from the HA 23, measuring RTT (Round Trip Time), and halving the measured value.
［数７］
　Tlowstt=Ts-Tdup1-Tdn+Tdup2-Tdn-(Tddn1-Tddn2)
　　　　=Ts+Tddn2-2Tdn-(Tddn1+Tdup1)+Tdup2
[Equation 7]
Tlowstt = Ts-Tdup1-Tdn + Tdup2-Tdn- (Tddn1-Tddn2)
= Ts + Tddn2-2Tdn- (Tddn1 + Tdup1) + Tdup2
　電話機能部１３３は、ハンドオーバ制御部１３６からハンドオーバ情報を取得すると、ハンドオーバ元およびハンドオーバ先の下りの絶対遅延時間Tddn1、Tddn2を比較し、Tddn1＞Tddn2、の場合は、取得した全てのハンドオーバ情報をハンドオーバ予告メッセージとして、ＨＡ２３を介して通信装置（ＣＮ）１２２に送信する。これにより、通信装置（ＣＮ）１２２において、無線通信装置（ＭＮ）１２１からのハンドオーバ情報、および上述したＨＡ２３との間の絶対遅延時間Tdnに基づいて、ハンドオーバによってロストすると思われる送信データを、当該通信装置（ＣＮ）１２２内に蓄積して、ハンドオーバ完了後に無線通信装置１２１で受信できるようにデータの送信を制御する。なお、上記のＨＡ２３との間の絶対遅延時間Tdnは、予め測定して通信装置（ＣＮ）１２２内に格納してもよいし、無線通信装置（ＭＮ）１２１からのハンドオーバ情報を受信して測定するようにしてもよい。 When the telephone function unit 133 obtains the handover information from the handover control unit 136, it compares the downlink absolute delay times Tddn1 and Tddn2 of the handover source and the handover destination, and if Tddn1> Tddn2, A handover notice message is transmitted to the communication device (CN) 122 via the HA 23. As a result, in the communication device (CN) 122, based on the handover information from the wireless communication device (MN) 121 and the absolute delay time Tdn with the HA 23 described above, the transmission data that is supposed to be lost due to the handover is Data is stored in the communication device (CN) 122 and data transmission is controlled so that the wireless communication device 121 can receive the data after the handover is completed. The absolute delay time Tdn with the HA 23 may be measured in advance and stored in the communication device (CN) 122, or measured by receiving handover information from the wireless communication device (MN) 121. You may make it do.
　以下、図２０に示した本実施の形態に係る通信装置（ＣＮ）１２２の構成および動作について説明する。 Hereinafter, the configuration and operation of the communication apparatus (CN) 122 according to the present embodiment shown in FIG. 20 will be described.
　図２４は、通信装置（ＣＮ）１２２の概略構成を示す機能ブロック図である。通信装置１２２は、図示しないインターネットサービスプロバイダを介してインターネット１８に接続するネットワークＩ／Ｆ（インターフェース）１８１と、ネットワークへの接続を制御する通信処理部１８２と、ＶｏＩＰのアプリケーションを実行する電話機能部１８３と、を有する。 FIG. 24 is a functional block diagram showing a schematic configuration of the communication device (CN) 122. The communication device 122 includes a network I / F (interface) 181 that connects to the Internet 18 via an Internet service provider (not shown), a communication processing unit 182 that controls connection to the network, and a telephone function unit that executes VoIP applications. 183.
　通信処理部１８２は、ネットワークＩ／Ｆ１８１のインターネット１８への接続を制御して、電話機能部１８３と無線通信装置１２１との間の通信を実行する。したがって、ネットワークＩ／Ｆ１８１および通信処理部１８２は、通信部を構成する。 The communication processing unit 182 controls the connection of the network I / F 181 to the Internet 18 and executes communication between the telephone function unit 183 and the wireless communication device 121. Therefore, the network I / F 181 and the communication processing unit 182 constitute a communication unit.
　図２５は、図２４に示した通信装置１２２の電話機能部１８３の概略構成を示す機能ブロック図である。電話機能部１８３は、例えばソフトフォンからなり、図１４に示した通信装置１２と同様に、公知のソフトフォンの構成である、ボタン入力部１４１、画面表示部１４２、マイク１４３、エンコーダ１４４、パケット送信部１４５、パケット受信部１４６、ジッタバッファ１４７、デコーダ１４８、スピーカ１４９、ジッタバッファ監視部１５０、ジッタバッファ制御部１５１、ＳＩＰ制御部１５２、および全体の動作を制御する全体制御部１５３を有する。なお、マイク１４３およびスピーカ１４９は、例えば、図２０に示したように送受話器１２２ａで構成される。 FIG. 25 is a functional block diagram showing a schematic configuration of the telephone function unit 183 of the communication device 122 shown in FIG. The telephone function unit 183 includes, for example, a soft phone, and has a configuration of a known soft phone, like the communication device 12 illustrated in FIG. 14, and includes a button input unit 141, a screen display unit 142, a microphone 143, an encoder 144, a packet The transmitter 145, the packet receiver 146, the jitter buffer 147, the decoder 148, the speaker 149, the jitter buffer monitor 150, the jitter buffer controller 151, the SIP controller 152, and the overall controller 153 that controls the overall operation. Note that the microphone 143 and the speaker 149 are configured by a handset 122a as shown in FIG. 20, for example.
　全体制御部１５３は、ボタン入力部１４１や画面表示部１４２を介して、ユーザの操作情報を取得し、その取得情報に基づいて全体の動作を制御する。また、ＳＩＰ制御部１５２は、通話の開始や終了のＳＩＰの手続きを制御する。通話中において、マイク１４３から取得された音声データは、符号化部であるエンコーダ１４４でエンコードされ、そのエンコードされたデータは、パケット送信部１４５からパケットに入れられて、通信処理部１８２およびネットワークＩ／Ｆ１８１を経て無線通信装置１２１へ送信される。 The overall control unit 153 acquires user operation information via the button input unit 141 and the screen display unit 142, and controls the overall operation based on the acquired information. The SIP control unit 152 controls SIP procedures for starting and ending a call. During a call, the audio data acquired from the microphone 143 is encoded by the encoder 144 which is an encoding unit, and the encoded data is put into a packet from the packet transmission unit 145, and the communication processing unit 182 and the network I The data is transmitted to the wireless communication apparatus 121 via / F181.
　また、通信処理部１８２を経てパケット受信部１４６で受信された無線通信装置１２１からのパケットは、ジッタバッファ１４７に一旦取り込まれてから読み出され、その読み出されたパケットは、デコーダ１４８でペイロード部分がデコードされて、スピーカ１４９から再生音声として出力される。なお、ジッタバッファ１４７のパケットの受信状況や、ジッタバッファ１４７内のパケット数（データ量）の状態は、ジッタバッファ監視部１５０で監視され、その監視結果に基づいて、ジッタバッファ制御部５１により、ジッタバッファ４７からのパケットの読み出し速度や、受信したパケットの破棄などの処理が制御される。 A packet from the wireless communication apparatus 121 received by the packet receiving unit 146 via the communication processing unit 182 is once taken into the jitter buffer 147 and read out. The read packet is loaded into the payload by the decoder 148. The portion is decoded and output as reproduced sound from the speaker 149. The reception status of packets in the jitter buffer 147 and the number of packets (data amount) in the jitter buffer 147 are monitored by the jitter buffer monitoring unit 150. Based on the monitoring result, the jitter buffer control unit 51 Processing such as a packet reading speed from the jitter buffer 47 and discarding of the received packet is controlled.
　図２０に示した通信装置１２２は、電話機能部１８３に、さらに、ハンドオーバ情報取得部１５５、送信制御部１５６および送信バッファ１５７を備える。すなわち、電話機能部１８３は、図３に示した第１実施の形態に係る無線通信装置１１の電話機能部３３と同様の構成を有する。 20 includes a telephone function unit 183, a handover information acquisition unit 155, a transmission control unit 156, and a transmission buffer 157. That is, the telephone function unit 183 has the same configuration as the telephone function unit 33 of the wireless communication apparatus 11 according to the first embodiment shown in FIG.
　ハンドオーバ情報取得部１５５は、無線通信装置１２１からのハンドオーバ予告メッセージを一定間隔毎に監視して、ハンドオーバの予定を決定するハンドオーバ予定決定情報を取得する。そして、ハンドオーバ予定決定情報が取得された場合は、ハンドオーバ情報取得部１５５は、さらに、無線通信装置１２１から所要のハンドオーバ情報を取得し、その取得した所要のハンドオーバ情報を送信制御部１５６に供給する。 The handover information acquisition unit 155 monitors handover notification messages from the wireless communication apparatus 121 at regular intervals, and acquires handover schedule determination information for determining a handover schedule. When the handover schedule determination information is acquired, the handover information acquisition unit 155 further acquires the required handover information from the radio communication apparatus 121 and supplies the acquired required handover information to the transmission control unit 156. .
　送信制御部１５６は、エンコーダ１４４による送信データの符号化ビットレートおよびエンコーダ１４４からパケット送信部１４５へのデータの送信を制御する。すなわち、送信制御部１５６は、ハンドオーバ情報取得部１５５からハンドオーバ情報が供給されない通常の通話状態では、エンコーダ４４でエンコードされたデータをパケット送信部１４５に直接送信する。これに対し、ハンドオーバ情報取得部１５５からハンドオーバ情報が供給された場合は、送信制御部１５６は、上記の絶対遅延時間Tdnを取得して、該絶対遅延時間Tdnとハンドオーバ情報とに基づいて、ハンドオーバによってロストすると思われるエンコーダ１４４からのデータを送信バッファ１５７に蓄積し、その蓄積したデータをハンドオーバ完了後にパケット送信部１４５に送信するように制御する。この送信制御部１５６による送信制御については、さらに後述する。 The transmission control unit 156 controls the encoding bit rate of transmission data by the encoder 144 and the transmission of data from the encoder 144 to the packet transmission unit 145. That is, the transmission control unit 156 directly transmits the data encoded by the encoder 44 to the packet transmission unit 145 in a normal call state in which handover information is not supplied from the handover information acquisition unit 155. On the other hand, when handover information is supplied from the handover information acquisition unit 155, the transmission control unit 156 acquires the absolute delay time Tdn and performs handover based on the absolute delay time Tdn and the handover information. Is stored in the transmission buffer 157, and the stored data is controlled to be transmitted to the packet transmission unit 145 after the handover is completed. The transmission control by the transmission control unit 156 will be described later.
　したがって、本実施の形態に係る通信装置１２２においてでは、電話機能部１８３は、リアルタイム通信系のアプリケーションを実行する実行部、および当該アプリケーションのデータの送信を制御する制御部を構成する。 Therefore, in communication apparatus 122 according to the present embodiment, telephone function unit 183 constitutes an execution unit that executes a real-time communication system application and a control unit that controls transmission of data of the application.
　次に、電話機能部１８３によるハンドオーバ時のデータ送信処理について説明する。 Next, data transmission processing at the time of handover by the telephone function unit 183 will be described.
　図２６は、電話機能部１８３によるハンドオーバ時のデータ送信処理の概要を説明するための図である。上述したように、通信装置（ＣＮ）１２２から送信するパケットは、無線通信装置（ＭＮ）１２１からのハンドオーバ予告メッセージMsg(HO)を受信した時点から、期間Tlowstt(sec)が経過したロスト期間Tlost（期間Ａ）でロストする。このため、この期間Ａにおいては、電話機能部１８３は、送信データの符号化ビットレートを下げるとともに、データを送信しながらそのコピーを送信バッファ１５７に蓄積する。 FIG. 26 is a diagram for explaining an outline of data transmission processing at the time of handover by the telephone function unit 183. As described above, the packet transmitted from the communication device (CN) 122 is the lost period Tlost in which the period Tlowstt (sec) has elapsed from the time when the handover notice message Msg (HO) is received from the wireless communication device (MN) 121. Lost in (period A). For this reason, during this period A, the telephone function unit 183 lowers the encoding bit rate of the transmission data and accumulates a copy thereof in the transmission buffer 157 while transmitting the data.
　その後、電話機能部１８３は、ハンドオーバ先からのパケットの送信が開始されたら、新しいデータを送信バッファ１５７内に蓄積しながら、送信バッファ１５７内のパケットが０となるまで、送信バッファ１５７内のデータを速く送信する（期間Ｂ）。その後、通信が終了するまで、あるいは、次のハンドオーバ予定による期間Ａが開始されるまでは、電話機能部１８３は、送信データを通常の符号化ビットレートでエンコードして、送信バッファ１５７に蓄積することなく送信する（期間Ｃ）。 Thereafter, when the transmission of the packet from the handover destination is started, the telephone function unit 183 stores the data in the transmission buffer 157 until the packet in the transmission buffer 157 reaches 0 while accumulating new data in the transmission buffer 157. Is transmitted quickly (period B). Thereafter, the telephone function unit 183 encodes the transmission data at the normal encoding bit rate and stores it in the transmission buffer 157 until the communication is completed or until the period A by the next handover schedule is started. (Period C).
　図２７は、電話機能部１８３の送信制御部１５６によるハンドオーバ時の動作を示すフローチャートである。以下、図２７に示すフローチャートを参照しながら、電話機能部１８３によるハンドオーバ時のデータ送信処理について、さらに詳細に説明する。 FIG. 27 is a flowchart showing the operation at the time of handover by the transmission control unit 156 of the telephone function unit 183. Hereinafter, the data transmission processing at the time of handover by the telephone function unit 183 will be described in more detail with reference to the flowchart shown in FIG.
　電話機能部１８３のハンドオーバ情報取得部１５５は、ＨＡ２３から転送される無線通信装置（ＭＮ）１２１からのハンドオーバ情報を一定間隔毎に監視する。その結果、ハンドオーバ予定決定情報を取得すると、所要のハンドオーバ情報である、ハンドオーバ準備時間Ts、ハンドオーバ元上り絶対遅延時間Tdup1およびTddn1、ハンドオーバ先上りおよび下り絶対遅延時間Tdup2およびTddn2、ハンドオーバ先予測帯域Rbdn2を取得して（ステップＳ１１１）、その取得した所要のハンドオーバ情報を送信制御部１５６に供給する。 The handover information acquisition unit 155 of the telephone function unit 183 monitors the handover information from the wireless communication device (MN) 121 transferred from the HA 23 at regular intervals. As a result, when the handover schedule determination information is acquired, the required handover information is the handover preparation time Ts, the handover source uplink absolute delay times Tdup1 and Tddn1, the handover destination uplink and downlink absolute delay times Tdup2 and Tddn2, the handover destination predicted bandwidth Rbdn2 Is acquired (step S111), and the acquired required handover information is supplied to the transmission control unit 156.
　送信制御部１５６は、ハンドオーバ情報を取得すると、先ず、ハンドオーバ予告メッセージMsg(HO)の受信時点からパケットロスが生じる期間Ａ（図２６参照）までの時間Tlowstt、期間Ａであるパケットのロスト期間Tlost、および、符号化ビットレートR1とを算出する（ステップＳ１１２）。 When the transmission control unit 156 acquires the handover information, first, the time Tlowstt from the time when the handover notice message Msg (HO) is received to the period A in which packet loss occurs (see FIG. 26), the lost period Tlost of the packet that is the period A And the encoding bit rate R1 are calculated (step S112).
　ここで、時間Tlowsttは、上記の数４で示した式に基づいて算出し、ロスト期間Tlostは、（Tddn1-Tddn2）から算出する。また、符号化ビットレートR1は、取得したRbdn2(bps)、通信装置１２２のハンドオーバ後の当該アプリケーションの標準再生速度Vnに対する再生速度Vf (sec/sec)、送信バッファ１５７の最大容量Sbf(bit)、ロスト期間Tlost(sec)、標準の符号化ビットレートRn(bps)、とするとき、（i）Sbf/ Tlost、（ii）Rbdn2/Vf、のうち、小さい方を上限として、取り得る符号化ビットレートの最大値を選択する。なお、ここで選択する符号化ビットレートは、帯域の変動等を考慮して、多少のマージンを持たせて、より低い符号化ビットレートを選択するようにしてもよい。また、ハンドオーバ後の再生速度Vfは、例えば、標準再生速度Vnの１．２５倍と予め設定して、両者で保持するか、あるいは通信装置１２２から無線通信装置１２１に事前に通知する。 Here, the time Tlowstt is calculated based on the equation shown in Equation 4 above, and the lost period Tlost is calculated from (Tddn1-Tddn2). Also, the encoding bit rate R1 is obtained Rbdn2 (bps), the reproduction speed Vf (sec / sec) with respect to the standard reproduction speed Vn of the application after the communication device 122 is handed over, and the maximum capacity Sbf (bit) of the transmission buffer 157 , Lost period Tlost (sec), standard encoding bit rate Rn (bps), and (i) Sbf / Tlost, (ii) Rbdn2 / Vf Select the maximum bit rate. It should be noted that the encoding bit rate selected here may be set to a lower encoding bit rate with some margin in consideration of band fluctuations and the like. Further, the reproduction speed Vf after the handover is set in advance as, for example, 1.25 times the standard reproduction speed Vn and is held by both, or notified from the communication apparatus 122 to the wireless communication apparatus 121 in advance.
　その後、送信制御部１５６は、Tlowstt時間待機し（ステップＳ１１３）、Tlowstt時間が経過すると（ロスト期間Tlostの開始）、エンコーダ１４４に対して、送信データの符号化ビットレートを算出した符号化ビットレートR1まで下げるように指示するとともに、エンコーダ１４４から受け取った送信データを、そのままパケット送信部１４５に渡しつつ、当該送信データをコピーして送信バッファ１５７に蓄積する（ステップＳ１１４）。なお、その際、送信データ中の一定（例えば、500msec）以上の長さの無音部分は、上記の一定の長さまで無音データを圧縮する。 Thereafter, the transmission control unit 156 waits for the Tlowstt time (step S113), and when the Tlowstt time has elapsed (start of the lost period Tlost), the encoding bit rate obtained by calculating the encoding bit rate of the transmission data to the encoder 144. The transmission data received from the encoder 144 is transferred to the packet transmission unit 145 as it is, and the transmission data is copied and stored in the transmission buffer 157 (step S114). At that time, the silence data having a length of a certain length (for example, 500 msec) or more in the transmission data is compressed to the above-mentioned length.
　上記のステップＳ１１４の処理は、ロスト期間Tlostが終了するまで行い（ステップＳ１１５）、ロスト期間Tlostが終了すると（Ｓ１１５のYes、期間Ｂの開始）、送信制御部１５６は、エンコーダ１４４から受け取った送信データをパケット送信部１４５に渡さずに、送信バッファ１５７に蓄積しながら、送信バッファ１５７に蓄積されているデータ（パケット）を古いものから、帯域に合わせてパケット送信部１４５に高速に渡して、無線通信装置（ＭＮ）１２１に送信する（ステップＳ１１６）。 The process of step S114 is performed until the lost period Tlost ends (step S115). When the lost period Tlost ends (Yes in S115, start of period B), the transmission control unit 156 transmits the transmission received from the encoder 144. While storing the data in the transmission buffer 157 without passing the data to the packet transmission unit 145, the data (packets) stored in the transmission buffer 157 is transferred from the oldest to the packet transmission unit 145 at a high speed according to the bandwidth. It transmits to the radio | wireless communication apparatus (MN) 121 (step S116).
　送信制御部１５６は、送信バッファ１５７内のパケット数を監視する（ステップＳ１１７）。その結果、送信バッファ１５７内のパケットが０になると（Ｓ１１７のYes、期間Ｃの開始）、送信制御部１５６は、エンコーダ１４４に符号化ビットレートを元に戻すように指示するとともに（ステップＳ１１８）、エンコーダ１４４からの送信データを送信バッファ１５７に蓄積することなく、パケット送信部１４５に渡して、無線通信装置（ＭＮ）１２１に送信する（ステップＳ１１９）。 The transmission control unit 156 monitors the number of packets in the transmission buffer 157 (step S117). As a result, when the packet in the transmission buffer 157 becomes 0 (Yes in S117, the start of period C), the transmission control unit 156 instructs the encoder 144 to restore the encoding bit rate (step S118). The transmission data from the encoder 144 is transferred to the packet transmission unit 145 without being stored in the transmission buffer 157 and transmitted to the wireless communication device (MN) 121 (step S119).
　図２８は、本実施の形態に係る通信装置１２２によりハンドオーバ時に送信制御を行った場合の無線通信装置における受信パケットの状態を示す図である。また、図２９は、図２８との比較のために、ハンドオーバ時に上記の送信制御を行わなかった場合の無線通信装置における受信パケットの状態を示す図である。図２８および図２９において、（ａ）は受信パケットのシーケンス番号、（ｂ）は単位時間の受信パケット数、（ｃ）は単位時間の受信データ量（byte）を示す。 FIG. 28 is a diagram illustrating a state of a received packet in the wireless communication device when transmission control is performed at the time of handover by the communication device 122 according to the present embodiment. For comparison with FIG. 28, FIG. 29 is a diagram illustrating a state of a received packet in the wireless communication apparatus when the above transmission control is not performed at the time of handover. 28 and 29, (a) shows the sequence number of the received packet, (b) shows the number of received packets per unit time, and (c) shows the received data amount (byte) per unit time.
　図２８および図２９の比較から明らかなように、本実施の形態に係る通信装置（ＣＮ）１２２は、ハンドオーバ時に無線通信装置（ＭＮ）１２１がロストするであろうパケットを、送信バッファ１５７に蓄積し、その蓄積したパケットを、無線通信装置（ＭＮ）１２１がハンドオーバした後に受信できるように送信するので、図２９（ａ）では生じていたパケットのロストが、図２８（ａ）では生じない。したがって、ハンドオーバ時でも、通信相手である無線通信装置（ＭＮ）１２１側では文章の連続性を保つことができるので、音声を聞くユーザに違和感を与えることもない。また、本実施の形態に係る通信装置（ＣＮ）１２２は、ロストするパケットを蓄積している間は、エンコーダ１４４による符号化ビットレートを落としているので、その後、蓄積されたパケットを、限られた帯域の中で滞留を起すことなく、通常より多く送信することができる。したがって、受信側の無線通信装置（ＭＮ）１２１では、図２８（ｂ）および（ｃ）に示す通常よりも多く受信されるパケットを、通常よりも高速に再生することで、本来の絶対遅延での再生に戻すことができる。また、送信バッファ１５７に蓄積するパケットを無音圧縮することにより、全体的なデータ容量を低減でき、より速く蓄積したパケットを送信することができる。 As is clear from the comparison between FIG. 28 and FIG. 29, the communication device (CN) 122 according to the present embodiment accumulates in the transmission buffer 157 packets that the wireless communication device (MN) 121 will lose at the time of handover. Then, since the accumulated packets are transmitted so that the wireless communication apparatus (MN) 121 can receive them after handover, the lost packets that occurred in FIG. 29A do not occur in FIG. Therefore, even at the time of handover, the continuity of the text can be maintained on the wireless communication device (MN) 121 side that is the communication partner, so that the user who listens to the voice does not feel uncomfortable. In addition, since the communication device (CN) 122 according to the present embodiment reduces the encoding bit rate by the encoder 144 while accumulating lost packets, the accumulated packets are limited thereafter. It is possible to transmit more than usual without causing retention in the band. Therefore, the receiving-side wireless communication device (MN) 121 reproduces packets received more than usual shown in FIGS. 28 (b) and (c) at a higher speed than usual, thereby achieving the original absolute delay. Can return to playback. Further, by silently compressing the packet stored in the transmission buffer 157, the overall data capacity can be reduced, and the stored packet can be transmitted faster.
　次に、図２０に示した無線通信装置（ＭＮ）１２１について、図３０および図３１を参照して、さらに詳細に説明する。 Next, the wireless communication device (MN) 121 shown in FIG. 20 will be described in more detail with reference to FIG. 30 and FIG.
　図３０は、無線通信装置１２１の電話機能部１３３の概略構成を示す機能ブロック図である。また、図３１は、電話機能部１３３の要部の動作を示すシーケンス図である。図３０に示すように、電話機能部１３３は、例えば、公知のソフトフォンからなり、図２５に示した通信装置１２２の電話機能部１８３と同様に、ボタン入力部２０１、画面表示部２０２、マイク２０３、エンコーダ２０４、パケット送信部２０５、パケット受信部２０６、ジッタバッファ２０７、デコーダ２０８、スピーカ２０９、ジッタバッファ監視部２１０、ジッタバッファ制御部２１１、ＳＩＰ制御部２１２、および全体の動作を制御する全体制御部２１３を有する。 FIG. 30 is a functional block diagram showing a schematic configuration of the telephone function unit 133 of the wireless communication apparatus 121. FIG. 31 is a sequence diagram showing the operation of the main part of the telephone function unit 133. As shown in FIG. 30, the telephone function unit 133 is made of, for example, a known soft phone, and similarly to the telephone function unit 183 of the communication apparatus 122 shown in FIG. 25, the button input unit 201, the screen display unit 202, the microphone 203, an encoder 204, a packet transmission unit 205, a packet reception unit 206, a jitter buffer 207, a decoder 208, a speaker 209, a jitter buffer monitoring unit 210, a jitter buffer control unit 211, a SIP control unit 212, and the whole for controlling the overall operation. A control unit 213 is included.
　全体制御部２１３は、ボタン入力部２０１や画面表示部２０２を介して、ユーザの操作情報を取得し、その取得情報に基づいて全体の動作を制御する。また、ＳＩＰ制御部２１２は、通話の開始や終了のＳＩＰの手続きを制御する。通話中において、マイク２０３から取得された音声データは、エンコーダ２０４でエンコードされ、そのエンコードされたデータは、パケット送信部２０５からパケットに入れられて、通信処理部１３４を経て通信装置１２２へ送信される。 The overall control unit 213 acquires user operation information via the button input unit 201 and the screen display unit 202, and controls the overall operation based on the acquired information. The SIP control unit 212 also controls SIP procedures for starting and ending a call. During a call, the audio data acquired from the microphone 203 is encoded by the encoder 204, and the encoded data is put into a packet from the packet transmission unit 205 and transmitted to the communication device 122 via the communication processing unit 134. The
　また、通信処理部１３４を経てパケット受信部２０６で受信された通信装置１２２からのパケットは、ジッタバッファ２０７に一旦取り込まれてから読み出され、その読み出されたパケットは、デコーダ２０８でペイロード部分がデコードされて、スピーカ２０９から再生音声として出力される。 Further, the packet from the communication device 122 received by the packet receiving unit 206 via the communication processing unit 134 is once fetched into the jitter buffer 207 and read out. Are decoded and output as reproduced sound from the speaker 209.
　ジッタバッファ監視部２１０は、図３１に示すように、ジッタバッファ２０７のパケットの受信状況や、ジッタバッファ２０７内のパケット数（データ量）の状態を監視し、その監視結果に基づいて、ジッタバッファ制御部２１１により、ジッタバッファ２０７からのパケットの読み出し速度や、受信したパケットの破棄などの処理を制御する。 As shown in FIG. 31, the jitter buffer monitoring unit 210 monitors the reception status of packets in the jitter buffer 207 and the number of packets (data amount) in the jitter buffer 207. Based on the monitoring result, the jitter buffer monitoring unit 210 The controller 211 controls processing such as the packet reading speed from the jitter buffer 207 and discarding of received packets.
　図２０に示した無線通信装置１２１は、図３０に示すように、電話機能部１３３に、さらに、ハンドオーバ情報取得部２１５および再生速度計算部２１６を備える。すなわち、電話機能部１３３は、図１４に示した通信装置１２の電話機能部８３と同様の構成を有する。 As shown in FIG. 30, the wireless communication apparatus 121 shown in FIG. 20 is further provided with a telephone function unit 133, a handover information acquisition unit 215, and a playback speed calculation unit 216. That is, the telephone function unit 133 has the same configuration as the telephone function unit 83 of the communication device 12 shown in FIG.
　図３１に示すように、ハンドオーバ情報取得部２１５は、ハンドオーバ制御部１３６からのハンドオーバ情報を一定間隔毎に監視し、ハンドオーバ情報があった場合は、上述したように、ハンドオーバ情報に含まれるハンドオーバ元およびハンドオーバ先の下りの絶対遅延時間Tddn1、Tddn2、を比較して、Tddn1＞Tddn2、の場合は、取得したハンドオーバ情報をハンドオーバ予告メッセージとして通信装置１２２に送信する。 As shown in FIG. 31, the handover information acquisition unit 215 monitors the handover information from the handover control unit 136 at regular intervals, and when there is handover information, as described above, the handover source included in the handover information And the absolute delay times Tddn1 and Tddn2 of the downlink of the handover destination are compared, and when Tddn1> Tddn2, the acquired handover information is transmitted to the communication device 122 as a handover notice message.
　また、ハンドオーバ情報取得部２１５は、ハンドオーバ情報を取得すると、Tddn1＞Tddn2、の場合は、さらにハンドオーバ情報に含まれるハンドオーバ完了通知を監視し、ハンドオーバ完了通知を受信すると、その旨を再生速度計算部２１６へ通知する。これにより、再生速度計算部２１６は、ジッタバッファ制御部２１１に標準再生速度Vnよりも速い所定の速度Vf（例えば、標準再生速度Vnの１．２５倍）で再生するように通知する。 Further, when the handover information is acquired, the handover information acquisition unit 215 further monitors the handover completion notification included in the handover information when Tddn1> Tddn2, and when receiving the handover completion notification, the reproduction speed calculation unit 216 is notified. As a result, the playback speed calculation unit 216 notifies the jitter buffer control unit 211 to play back at a predetermined speed Vf that is faster than the standard playback speed Vn (for example, 1.25 times the standard playback speed Vn).
　その後、再生速度計算部２１６は、一定間隔でジッタバッファ監視部２１０からジッタバッファ２０７内のパケット蓄積量とパケット受信間隔とを取得し、パケット受信間隔が標準再生速度Vnの受信間隔に対応する一定以上で、かつパケット蓄積量が標準のパケット蓄積量以下になると、通常の再生制御に戻すようにジッタバッファ制御部２１１に指示する。 Thereafter, the playback speed calculation unit 216 acquires the packet accumulation amount and the packet reception interval in the jitter buffer 207 from the jitter buffer monitoring unit 210 at regular intervals, and the packet reception interval corresponds to the reception interval of the standard playback speed Vn. When the packet accumulation amount is equal to or less than the standard packet accumulation amount as described above, the jitter buffer control unit 211 is instructed to return to the normal reproduction control.
　なお、ハンドオーバ情報取得部２１５は、取得したハンドオーバ情報に含まれるハンドオーバ元およびハンドオーバ先の下りの絶対遅延時間Tddn1、Tddn2が、Tddn1≦Tddn2、の場合は、ハンドオーバによるパケットロスは発生しないので、この場合は、通信装置１２２にハンドオーバ予告メッセージを送信しないとともに、ハンドオーバ完了通知を受信しても、その旨を再生速度計算部２１６へ通知しない。したがって、この場合は、ジッタバッファ制御部２１１は、ジッタバッファ監視部２１０による監視結果に基づいて、ジッタバッファ２０７内のパケットを通常の制御で再生することになる。 The handover information acquisition unit 215 does not generate a packet loss due to handover when the absolute delay times Tddn1 and Tddn2 of the handover source and the handover destination included in the acquired handover information are Tddn1 ≦ Tddn2. In this case, the handover notification message is not transmitted to the communication device 122, and even when the handover completion notification is received, the playback speed calculation unit 216 is not notified of this. Therefore, in this case, the jitter buffer control unit 211 reproduces the packet in the jitter buffer 207 by normal control based on the monitoring result by the jitter buffer monitoring unit 210.
　図３２は、上述した無線通信装置１２１によるパケットの再生制御を説明するための図で、図３２（ａ）は、ジッタバッファ２０７が単位時間に受信するパケット数、図３２（ｂ）は、ジッタバッファ２０７内のパケット蓄積量、図３２（ｃ）は、再生速度を示す。上述したように、通信装置１２２は、ハンドオーバによってロストすると思われる送信データを蓄積して、ハンドオーバ完了後に無線通信装置１２１で受信できるタイミングでデータを高速に送信する。 FIG. 32 is a diagram for explaining packet reproduction control by the wireless communication apparatus 121 described above. FIG. 32A shows the number of packets received by the jitter buffer 207 per unit time, and FIG. 32B shows jitter. The amount of packets stored in the buffer 207, FIG. 32 (c), shows the playback speed. As described above, the communication device 122 accumulates transmission data that is supposed to be lost due to handover, and transmits the data at a high speed at a timing that can be received by the wireless communication device 121 after the handover is completed.
　したがって、図３２（ａ）に示すように、ＨＡ２３からハンドオーバ完了情報を受信した直後は、一時的に単位時間の受信パケット数が増加し、その増加に応じて、図３２（ｂ）に示すように、ジッタバッファ２０７内のパケット蓄積量も漸増する。しかし、図３２（ｃ）に示すように、再生速度は、ＨＡ２３からハンドオーバ完了情報を受信すると、標準再生速度Vnよりも速い速度Vfとするので、ジッタバッファ２０７内のパケット蓄積量は、単位時間の受信パケット数が標準に戻った後は漸減し、標準蓄積量になると、再生速度も標準再生速度Vnに戻る。 Therefore, as shown in FIG. 32A, immediately after receiving the handover completion information from the HA 23, the number of received packets per unit time temporarily increases, and as shown in FIG. In addition, the amount of packets stored in the jitter buffer 207 gradually increases. However, as shown in FIG. 32 (c), when the handover speed is received from the HA 23, the playback speed is set to a speed Vf higher than the standard playback speed Vn. Therefore, the packet accumulation amount in the jitter buffer 207 is unit time. After the number of received packets returns to the standard, it gradually decreases, and when the standard accumulation amount is reached, the playback speed also returns to the standard playback speed Vn.
　以上の処理により、ＨＡ２３からのハンドオーバ完了情報を受信した後に、通信装置１２２から、蓄積されたパケットが高速に到着するという状態に適切に対応して、最適な速度でパケットを再生することができる。 Through the above processing, after receiving the handover completion information from the HA 23, it is possible to reproduce the packet at the optimum speed appropriately corresponding to the state where the accumulated packet arrives at high speed from the communication device 122. .
　上述したように、無線通信装置（ＭＮ）１２１は、ハンドオーバの予定を決定すると、本実施の形態に係る通信装置（ＣＮ）１２２にハンドオーバ予告メッセージを送信する。そして、通信装置１２２は、無線通信装置１２１からのハンドオーバ予告メッセージを受信して、該ハンドオーバ予告メッセージに含まれるハンドオーバ情報に基づいて、ハンドオーバによってロストすると思われる送信データを推定し、その推定した送信データを送信バッファ１５７に蓄積して、ハンドオーバ完了後に、無線の帯域に合わせた速度で無線通信装置１２１に送信する。 As described above, when the wireless communication device (MN) 121 determines a handover schedule, the wireless communication device (MN) 121 transmits a handover notification message to the communication device (CN) 122 according to the present embodiment. Then, the communication device 122 receives the handover advance notice message from the wireless communication device 121, estimates transmission data that is thought to be lost due to the handover based on the handover information included in the handover advance notice message, and the estimated transmission Data is stored in the transmission buffer 157, and is transmitted to the wireless communication apparatus 121 at a speed matching the wireless band after the handover is completed.
　ここで、送信バッファ１５７による送信データの蓄積開始は、受信したハンドオーバ予告メッセージのタイミングを基準に、ロストすると思われる送信データの蓄積開始のタイミングを送信制御部１５６で算出して決定される。このため、ロストすると思われるパケットを、より正確に推定して蓄積するには、送信制御部１５６で算出した蓄積開始のタイミングと、無線通信装置１１が実際に行うハンドオーバによって生じるロストのタイミングとを、正確に一致させるのが好適である。その方法として、下記の２つの方法が考えられる。 Here, the transmission data accumulation start by the transmission buffer 157 is determined by the transmission control unit 156 calculating the transmission data accumulation start timing that is considered to be lost based on the timing of the received handover notice message. For this reason, in order to more accurately estimate and accumulate the packet that seems to be lost, the accumulation start timing calculated by the transmission control unit 156 and the lost timing generated by the handover actually performed by the wireless communication apparatus 11 are set. It is preferable to make them match exactly. As the method, the following two methods can be considered.
（１）通信装置１２２の送信バッファ１５７が蓄積処理を開始するタイミングに合わせて、蓄積開始のメッセージが通信装置１２２に到達するように、無線通信装置１２１から蓄積開始メッセージを送出する。
（２）通信装置１２２の計時周期を無線通信装置１２１の計時周期に同期させる。 (1) The accumulation start message is transmitted from the wireless communication apparatus 121 so that the accumulation start message reaches the communication apparatus 122 at the timing when the transmission buffer 157 of the communication apparatus 122 starts the accumulation process.
(2) The timing cycle of the communication device 122 is synchronized with the timing cycle of the wireless communication device 121.
　上記（１）を採用する場合は、蓄積開始のタイミングから、無線通信装置１２１から通信装置１２２への伝送遅延時間分前に、無線通信装置１２１から通信装置１２２に向けて蓄積開始メッセージを送出すればよい。このように、無線通信装置１２１における計時で、ハンドオーバを行うようにすれば、理論上誤差はないことになる。 When the above (1) is adopted, an accumulation start message is sent from the wireless communication apparatus 121 to the communication apparatus 122 before the transmission delay time from the wireless communication apparatus 121 to the communication apparatus 122 from the accumulation start timing. That's fine. In this way, if handover is performed during the time measurement in the wireless communication apparatus 121, there is no theoretical error.
　しかし、ハンドオーバは、無線の通信状態が悪化する方向にあるために行うということを考えると、ハンドオーバを行う時間付近においては、通信経路上でパケットの滞留が生じることが想定される。このようにパケットの滞留が生じると、上記の蓄積開始メッセージは、滞留のために、予定したタイミングで通信装置１２２に到達することが不可能になる（無線通信装置１２１から通信装置１２２への上りの滞留は、無線通信装置１２１では計測できない）。 However, considering that handover is performed because the wireless communication state tends to deteriorate, it is assumed that packets stay on the communication path near the time when handover is performed. When packet retention occurs in this way, the above accumulation start message cannot reach the communication device 122 at a scheduled timing due to retention (upstream from the wireless communication device 121 to the communication device 122). ) Cannot be measured by the wireless communication device 121).
　以上のことを考慮すると、無線通信装置１２１からは、事前のハンドオーバ予告メッセージと、直前の蓄積開始メッセージの双方を送出するようにし、通信装置１２２では、パケットの受信状態から滞留の監視を行い、滞留が生じていないと判断した場合には、直前の蓄積開始メッセージを優先し、滞留が生じていると判断した場合には、ハンドオーバ予告メッセージに基づいて予定した蓄積開始タイミングに対応して、蓄積を開始するようにするのが好ましい。 Considering the above, the wireless communication device 121 sends both a prior handover notice message and a previous accumulation start message, and the communication device 122 monitors the stay from the reception state of the packet, When it is determined that no retention has occurred, priority is given to the previous accumulation start message, and when it is determined that retention has occurred, accumulation is performed in accordance with the scheduled accumulation start timing based on the handover notice message. It is preferable to start.
　上記（２）を採用する場合は、無線通信装置１２１と通信装置１２２との計時周期を事前に同期させる必要がある。その同期方法としては、例えば、通信装置１２２により、無線通信装置１２１からの無線状態を一定期間受信して、無線状態が良いと判断される状態で、ＲＴＰパケットの受信周期を計測し、その計測した受信周期を補正周期として用いて、通信装置１２２の計時周期を無線通信装置１２１に同期させることが考えられる。これにより、通信装置１２２では、無線通信装置１２１で算出された蓄積開始タイミングを補正して蓄積を開始することができる。 When adopting the above (2), it is necessary to synchronize the timing periods of the wireless communication device 121 and the communication device 122 in advance. As the synchronization method, for example, the communication device 122 receives the wireless state from the wireless communication device 121 for a certain period, measures the RTP packet reception period in a state where the wireless state is determined to be good, and performs the measurement. It is conceivable to synchronize the timing period of the communication apparatus 122 with the wireless communication apparatus 121 using the received reception period as the correction period. Accordingly, the communication device 122 can start accumulation by correcting the accumulation start timing calculated by the wireless communication device 121.
　このように、無線通信装置１２１からのＲＴＰパケットを用いて通信装置１２２の計時周期を補正すれば、例えば、ＶｏＩＰのアプリケーションでは、基本的に音声のＲＴＰパケットは一定周期で送出され、無線状態が良好な場合はジッタが小さいので、無線通信装置１２１と通信装置１２２との計時周期を正確に同期させることができる。 In this way, if the timing cycle of the communication device 122 is corrected using the RTP packet from the wireless communication device 121, for example, in a VoIP application, basically, an audio RTP packet is transmitted at a constant cycle, and the wireless state is When it is favorable, the jitter is small, so that the timing periods of the wireless communication device 121 and the communication device 122 can be accurately synchronized.
　なお、上記（１）または（２）のいずれを採用する場合でも、無線通信装置１２１側において、ハンドオーバの予定が変更された場合は、その旨のメッセージを無線通信装置１２１から通信装置１２２に送出して、ハンドオーバの予定変更に応じて通信装置１２２の動作を修正する。例えば、無線通信装置１２１は、通信装置１２２にハンドオーバ予告メッセージを送出した後、ハンドオーバ前に、無線通信装置１２１に到着したパケットから、滞留が生じていることを検知した場合は、通信装置１２２に滞留発生のメッセージを送出する。また、通信装置１２２は、蓄積開始タイミング前に滞留発生のメッセージを受信した場合は、設定している最大蓄積時間（送信バッファ１５７の最大容量Sbf）を越えない範囲で、想定される蓄積容量をさらに増やして、当初の蓄積開始タイミングから前に遡ったタイミングで蓄積を開始する。そして、増量した蓄積時間にて、符号化ビットレートを再計算する。 In either case of adopting the above (1) or (2), if the handover schedule is changed on the wireless communication apparatus 121 side, a message to that effect is sent from the wireless communication apparatus 121 to the communication apparatus 122. Then, the operation of the communication device 122 is corrected according to the scheduled change of the handover. For example, if the wireless communication apparatus 121 detects that a stagnation has occurred from a packet that has arrived at the wireless communication apparatus 121 before the handover after sending a handover notification message to the communication apparatus 122, the wireless communication apparatus 121 A message indicating the occurrence of stagnation is sent. In addition, when the communication device 122 receives a retention occurrence message before the accumulation start timing, the communication apparatus 122 sets an estimated accumulation capacity within a range not exceeding the set maximum accumulation time (the maximum capacity Sbf of the transmission buffer 157). Further increase, and accumulation starts at a timing going back from the initial accumulation start timing. Then, the encoding bit rate is recalculated with the increased accumulation time.
　例えば、図２３において、ハンドオーバ予告メッセージMsg(HO)の受信時に、ハンドオーバ元とハンドオーバ先の伝送遅延差によるパケットのロストが２００(msec)であった場合、蓄積時間Tlostは、２００(msec)に設定される。この状態で、蓄積開始タイミングT1から５００(msec)手前の時点で、無線通信装置１２１から滞留発生メッセージを受信した場合は、想定される最大蓄積時間は、２００＋５００＝７００(msec)、となる。この場合、送信バッファ１５７の最大容量Sbfが、５００(msec)に設定されていれば、蓄積時間が５００(msec)となるように、先の蓄積開始タイミングT1に対して、増量した３００(msec)分遡った（T1－３００）(msec)のタイミングで蓄積を開始する。 For example, in FIG. 23, when the handover notice message Msg (HO) is received and the lost packet due to the transmission delay difference between the handover source and the handover destination is 200 (msec), the accumulation time Tlost is set to 200 (msec). Is set. In this state, if a stay occurrence message is received from the wireless communication apparatus 121 at a time point 500 (msec) before the accumulation start timing T1, the assumed maximum accumulation time is 200 + 500 = 700 (msec). In this case, if the maximum capacity Sbf of the transmission buffer 157 is set to 500 (msec), the amount is increased by 300 (msec) with respect to the previous accumulation start timing T1 so that the accumulation time becomes 500 (msec). ) Accumulation starts at the timing of (T1-300) (msec) retroactive.
　このように、ハンドオーバ付近で、無線経路上でパケットの滞留が生じている場合は、その滞留分を含めてパケットを蓄積して、その蓄積したパケットをハンドオーバ先の経路を用いて送信することにより、ハンドオーバ元の滞留による無通状態（間隙）自体は補うことはできないが、その間にロストするパケット数を低減することが可能となる。 As described above, when packet retention occurs on the wireless route near the handover, the packet is accumulated including the remaining amount, and the accumulated packet is transmitted using the handover destination route. The non-transmission state (gap) itself due to the retention of the handover source cannot be compensated for, but the number of lost packets during that time can be reduced.
　なお、本発明は、上記実施の形態にのみ限定されるものではなく、幾多の変形または変更が可能である。例えば、第１実施の形態に係る無線通信装置１１の電話機能部３３に、図３０に示した無線通信装置１２１の電話機能部１３３が有する再生速度計算部２１６を付加して、ハンドオーバの際に上述した送信制御と再生制御との双方を実行する無線通信装置を構成することができる。同様に、第２実施の形態に係る通信装置１２２の電話機能部１８３に、図１４に示した通信装置１２の電話機能部８３が有する再生速度計算部１１６を付加して、ハンドオーバの際に上述した送信制御と再生制御との双方を実行する通信装置を構成することができる。 It should be noted that the present invention is not limited to the above embodiment, and many variations or modifications are possible. For example, a playback speed calculation unit 216 included in the telephone function unit 133 of the wireless communication apparatus 121 shown in FIG. 30 is added to the telephone function unit 33 of the wireless communication apparatus 11 according to the first embodiment, and at the time of handover. A wireless communication apparatus that performs both the transmission control and the reproduction control described above can be configured. Similarly, a playback speed calculation unit 116 included in the telephone function unit 83 of the communication apparatus 12 illustrated in FIG. 14 is added to the telephone function unit 183 of the communication apparatus 122 according to the second embodiment, and the above-described operation is performed at the time of handover. It is possible to configure a communication device that performs both transmission control and reproduction control.
　また、本発明は、ＶｏＩＰのアプリケーションを実行する場合に限らず、映像や音楽等のマルチメディアデータをストリーミング送信する場合のようなリアルタイム通信系のアプリケーションを実行する場合にも有効に適用できる。この場合は、アプリケーションの実行部を、電話機能部に代えて、同様の送信制御機能を有するマルチメディア機能部で構成すればよい。さらに、本発明は、ｃｄｍａ２０００ １ｘＥＶ－ＤＯと無線ＬＡＮとの間のハンドオーバに限らず、他の無線通信ネットワーク、例えば、ＰＤＣ（Personal Digital Cellular）、Ｗ－ＣＤＭＡ（Wideband CDMA）、ＰＨＳ（Personal Handy-phone System）、Bluetooth、ＷｉＭＡＸ、ＬＴＥ(Long Term Evolution)、ＵＭＢ(Ultra Mobile Broadband)、ＩＭＴ－Ａｄｖａｎｃｅｄ等の任意の異なる無線通信ネットワーク間でのハンドオーバの際にも有効に適用することができる。 Further, the present invention is not limited to the case of executing a VoIP application, but can be effectively applied to the case of executing a real-time communication application such as streaming transmission of multimedia data such as video and music. In this case, the application execution unit may be configured by a multimedia function unit having a similar transmission control function instead of the telephone function unit. Further, the present invention is not limited to handover between cdma2000 1xEV-DO and a wireless LAN, but other wireless communication networks such as PDC (Personal Digital Cellular), W-CDMA (Wideband） CDMA), PHS (Personal Handy- The present invention can be effectively applied to handover between any different wireless communication networks such as phone (System), Bluetooth, WiMAX, LTE (Long Term Evolution), UMB (Ultra Mobile Broadband), and IMT-Advanced.

Claims (9)

  1. 　第１無線通信ネットワーク、および該第１無線通信ネットワークと異なる第２無線通信ネットワークに接続して無線通信を実行する無線通信部と、
    　該無線通信部を介してリアルタイム通信系のアプリケーションを実行する実行部と、
    　前記第１無線通信ネットワークに接続して前記アプリケーションを実行中に、当該第１無線通信ネットワークにおける無線リンクの通信品質を取得する通信品質取得部と、
    　該通信品質取得部により取得した前記通信品質に基づいて、前記第１無線通信ネットワークから前記第２無線通信ネットワークへのハンドオーバの準備を開始するか否かを決定する決定部と、
    　前記決定部によりハンドオーバ準備の開始を決定すると、前記第１無線通信ネットワークを介してデータを送信するとともに、該データを所定時間蓄積し、ハンドオーバ後に、該蓄積したデータを前記第２無線通信ネットワークを介して送信するよう制御する制御部と、
    　を備えることを特徴とする無線通信装置。     A wireless communication unit that performs wireless communication by connecting to a first wireless communication network and a second wireless communication network different from the first wireless communication network;
    An execution unit that executes an application of a real-time communication system via the wireless communication unit;
    A communication quality acquisition unit for acquiring communication quality of a radio link in the first wireless communication network while executing the application by connecting to the first wireless communication network;
    A determination unit that determines whether to start preparation for handover from the first wireless communication network to the second wireless communication network based on the communication quality acquired by the communication quality acquisition unit;
    When the determination unit determines the start of handover preparation, the data is transmitted through the first wireless communication network, the data is stored for a predetermined time, and after the handover, the stored data is transferred to the second wireless communication network. A control unit controlling to transmit via,
    A wireless communication apparatus comprising:
  2. 　前記アプリケーションの実行中に、前記決定部がハンドオーバ準備の開始を決定すると、前記通信品質取得部が取得した通信品質に基づいてハンドオーバを開始するまでのハンドオーバ準備時間を推定する推定部と、
    　前記決定部がハンドオーバ準備の開始を決定すると、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間を計測する計測部と、を備え、
    　前記制御部は、前記計測部により計測した前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間と、前記推定部により推定した前記ハンドオーバ準備時間とに基づいて、前記データを蓄積する開始時間を決定することを特徴とする請求項１に記載の無線通信装置。     When the determination unit determines the start of handover preparation during the execution of the application, an estimation unit that estimates a handover preparation time until the handover is started based on the communication quality acquired by the communication quality acquisition unit;
    When the determination unit determines the start of handover preparation, a measurement unit that measures respective delay times in the first wireless communication network and the second wireless communication network, and
    The control unit accumulates the data based on respective delay times in the first wireless communication network and the second wireless communication network measured by the measurement unit and the handover preparation time estimated by the estimation unit. The wireless communication apparatus according to claim 1, wherein a start time to be determined is determined.
  3. 　前記決定部がハンドオーバ準備の開始を決定すると、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間を計測する計測部と、を備え、
    　前記制御部は、前記計測部により計測した前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間に基づいて、前記データを蓄積する所定時間を決定することを特徴とする請求項１に記載の無線通信装置。     When the determination unit determines the start of handover preparation, a measurement unit that measures respective delay times in the first wireless communication network and the second wireless communication network, and
    The said control part determines the predetermined time which accumulate | stores the said data based on each delay time in the said 1st radio | wireless communication network and the said 2nd radio | wireless communication network measured by the said measurement part. The wireless communication device according to 1.
  4. 　送信データを符号化する符号化部を備え、
    　該符号化部は、前記決定部がハンドオーバ準備の開始を決定する前の符号化ビットレートよりも低いレートで、前記蓄積するデータを符号化することを特徴とする請求項１，２または３に記載の無線通信装置。     An encoding unit for encoding transmission data;
    4. The encoding unit according to claim 1, 2 or 3, wherein the encoding unit encodes the accumulated data at a rate lower than an encoding bit rate before the determination unit determines start of handover preparation. The wireless communication device described.
  5. 　通信ネットワークに接続して通信を実行する通信部と、
    　該通信部を介してリアルタイム通信系のアプリケーションを実行する実行部と、
    　前記アプリケーションの通信相手である無線通信装置が、通信中の第１無線通信ネットワークから該第１無線通信ネットワークと異なる第２無線通信ネットワークヘハンドオーバするハンドオーバの情報を前記無線通信装置から受信すると、前記通信ネットワークを介してデータを送信するとともに、該データを所定時間蓄積し、前記無線通信装置のハンドオーバ後に、該蓄積したデータを前記無線通信装置へ送信するよう制御する制御部と、
    　を備えることを特徴とする通信装置。     A communication unit that connects to a communication network and executes communication;
    An execution unit that executes an application of a real-time communication system via the communication unit;
    When a wireless communication device that is a communication partner of the application receives handover information from the wireless communication device that performs handover from the first wireless communication network in communication to a second wireless communication network different from the first wireless communication network, A control unit for transmitting data via a communication network, storing the data for a predetermined time, and controlling the stored data to be transmitted to the wireless communication device after handover of the wireless communication device;
    A communication apparatus comprising:
  6. 　前記制御部は、前記ハンドオーバの情報に含まれる、ハンドオーバの準備時間と、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間と、前記通信ネットワークにおける遅延時間とに基づいて、前記データを蓄積する開始時間を決定することを特徴とする請求項５に記載の通信装置。 The control unit, based on the handover preparation time, the delay time in the first radio communication network and the second radio communication network, and the delay time in the communication network, included in the handover information, The communication apparatus according to claim 5, wherein a start time for storing the data is determined.
  7. 　前記制御部は、前記ハンドオーバの情報に含まれる、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間に基づいて、前記データを蓄積する所定時間を決定することを特徴とする請求項５に記載の通信装置。 The control unit determines a predetermined time for storing the data based on respective delay times in the first wireless communication network and the second wireless communication network included in the handover information. The communication device according to claim 5.
  8. 　前記制御部は、前記ハンドオーバの情報に含まれる、前記第１無線通信ネットワークおよび前記第２無線通信ネットワークにおけるそれぞれの遅延時間に基づいて、前記データを蓄積する所定時間を決定することを特徴とする請求項６に記載の通信装置。 The control unit determines a predetermined time for storing the data based on respective delay times in the first wireless communication network and the second wireless communication network included in the handover information. The communication apparatus according to claim 6.
  9. 　送信データを符号化する符号化部を備え、
    　前記符号化部は、前記ハンドオーバの情報を受信する前の符号化ビットレートよりも低いレートで、前記蓄積するデータを符号化することを特徴とする請求項５，６，７または８に記載の通信装置。     An encoding unit for encoding transmission data;
    9. The encoding unit according to claim 5, 6, 7 or 8, wherein the encoding unit encodes the accumulated data at a rate lower than an encoding bit rate before receiving the handover information. Communication device.
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